An April 2023 study from Kent State University found that remote workers are more likely to be vigilant of security threats and take actions to ward them off than their in-office counterparts.

Thursday, April 4, 2024 14:00

As my manager knows, I’m not the biggest fan of working in a physical office. I’m a picky worker — I like my workspace to be borderline frigid, I hate dark mode on any software, and I want any and all lighting cranked all the way up.  

So, know that I’m biased going into this, but I also can’t get over the idea that companies are using cybersecurity as an excuse to create return-to-office policies in 2024.  

I started thinking about this because of the video game developer Rockstar, which owns some of the largest video game franchises on the planet like Red Dead Redemption and Grant Theft Auto. 

The company recently started asking its employees to return to its physical office five days a week in the name of productivity and security as the company pushes to finish its highly anticipated title “Grand Theft Auto VI.”  

Rockstar has long faced a number of cybersecurity concerns over the years, including a massive leak featuring early, in-progress gameplay of GTA VI in 2022 and other sensitive data. The attack was eventually attributed to the Lapsus$ group, and the perpetrator was eventually charged and sentenced. The first reveal trailer for the game was also leaked ahead of time.  

Many other companies have started to implement return-to-office policies over the past two years, citing various things ranging from worker productivity to interpersonal camaraderie, real estate costs, and more. I’m willing to hear arguments for all those things, but simply thinking that having employees all in one physical space is going to solve security problems seems far-fetched to me.  

We’ve written and talked about the various ways remote work has influenced cybersecurity since the onset of the COVID-19 pandemic. There’s no doubt that admins have had to implement new login methods, security controls and policies since more workers across the globe started working remotely. But four years into this trend, there’s no excuse to not be prepared to have remote workers anymore. 

An April 2023 study from Kent State University found that remote workers are more likely to be vigilant of security threats and take actions to ward them off than their in-office counterparts.  

The use of multi-factor authentication during the rise in remote work has skyrocketed, but often, this requirement is actually dropped if a user is physically in the office or accessing an on-site machine because of the perceived security of being in the office.  

The perceived security of a physical office can sometimes lull admins into a false sense of security, too, because machines located on-site may lack pre-boot authentication or encryption that’s commonly found on remote workers’ devices.  

I’m not saying that working in an office is inherently less secure than remote work, but I do believe that the risks are essentially the same. Regardless of where an employee is working from, they should be using app-based MFA to access all their services. Sensitive software and hardware should rely on passkeys or physical token access rather than outdated password policies that create easy-to-guess or shareable text-based passwords.  

And if security is the name of the game when asking employees to come back into the office, there’s still going to be a monetary investment that comes with that, too. 

Cisco’s recently published Global Hybrid Work study found that only 28 percent of responding employees say they would rank their employers’ office’s “Privacy and security features” as “very well.” To me, that says that even if employers want workers back in the office, they still need to upgrade their security, which is always going to mean more money and greater manpower.  

Security fundamentals should stay the same, no matter where your employees are. And suppose security is a chief concern for a company in wanting to go back to the “traditional” office lifestyle. In that case, I’m willing to bet they still have security gaps to overcome that simply can’t be solved by thinking they’ll be able to keep a closer eye on employees while they’re in the office to keep them from clicking on a phishing email. 

**The one big thing **

Remote system management/desktop access tools such as AnyDesk and TeamViewer have grown in popularity since 2020. While there are many legitimate uses for this software, adversaries are also finding ways to use them for command and control in their campaigns. Cisco Talos Incident Response (Talos IR) has recently seen a spike in actors using this type of software as a method of gaining initial access to a network or to spy on the actions of users. Talos IR noted in its Quarterly Trends report for the third quarter of 2023, “AnyDesk was observed in all ransomware and pre-ransomware engagements \[. . .\], underscoring its role in ransomware affiliates' attack chains.” 

**Why do I care? **

The use of these types of tools has increased since the start of the COVID-19 pandemic when remote work became more common. Since this software is legitimate, it can be easy for an attacker to compromise it and sit undetected on a network, bypassing traditional blocking methods. These tools introduce the ability for an adversary to potentially take full remote control of a system, are easy to download and install, and can be very difficult to detect since they are considered legitimate software. 

**So now what? **

Adopting one, or at most two, approved remote management solutions will allow the organization to thoroughly test and deploy in the most secure possible configuration. Once a solution is approved and championed for the organization, other remote management/access tools should be explicitly banned by policy. Due to the complexity of implementing all these controls, detection rules can serve as a backup in case an adversary finds a way to circumvent these mitigations. 

**Top security headlines of the week **

**The U.S. and Britain have jointly filed chargers and sanctions against a Chinese state-sponsored actor known as APT31.** The group is accused of a sweeping espionage campaign allegedly linked to China's Ministry of State Security (MSS) in the province of Hubei. The group reportedly targeted thousands of U.S. and foreign politicians, foreign policy experts and other high-profile targets. Individuals in the White House, U.S. State Department and spouses of officials were also among those targeted. The attacks aligned with geopolitical events affecting China, including economic tensions with the U.S., arguments over control of the South China Sea, and pro-democracy rallies in Hong Kong in 2019. A release from the U.S. Department of Justice stated that the campaigns involved more than 10,000 malicious emails, sent to targets in multiple continents, in what it called a “prolific global hacking operation.” The charges go on to say that APT31 hoped to compromise government institution networks and stealing trade secrets. Seven Chinese nationals are the target of the new sanctions for their alleged involvement with APT31, including the Wuhan XRZ corporation that is tied to the threat actor. (Reuters, U.S. Department of Justice) 

**A silent backdoor on Linux machines was almost a massive supply chain attack, before a lone developer found malicious code hidden in software updates.** The malicious code was hidden in two updates to xz Utils, an open-source data compression utility available on almost all installations of Linux and other Unix-like operating systems. Had it been successfully deployed, adversaries could have stashed malicious code in an SSH login certificate, upload it and execute it on the backdoored device. Whoever is behind this code likely spent years working on it, with open-source updates going back to 2021. The actor never actually took advantage of the malicious code, so it’s unclear what they planned to upload. Researchers eventually identified the vulnerability as CVE-2024-3094. The U.S. Cybersecurity and Infrastructure Security Agency warned government agencies to downgrade their xz Utils to older versions. (Ars Technica, Dark Reading) 

**There is a massive backup with the National Vulnerabilities Database and, consequently, MITRE is unable to compile a list of all new vulnerabilities.** A recent study from Flashpoint found that there was backlog of more than 100,000 vulnerabilities with no CVE number, and consequently, hadn’t been included in the NVD. Of those, 330 vulnerabilities had been exploited in the wild, yet defenders had not been made aware of them. The National Institute of Standards and Technology blamed the backup on an increase in the volume of software available to the public, leading to a larger number of vulnerabilities, as well as “a change in interagency support.” NIST has only analyzed about half of the more than 8,700 vulnerabilities that had been submitted so far in 2024. And in March alone, they only analyzed 199 out of the 3,370 vulnerabilities submitted. Several organizations have tried launching their own alternatives to the NVD, though adoption can still take a long time. NIST has also vowed to remain dedicated to the NVD and that it’s still regrouping its current efforts. (SecurityWeek, The Record by Recorded Future) 

**Can’t get enough Talos? **

*   Enterprise Imperatives: The Critical Importance of Threat Intelligence 
*   Beware the gap between security readiness and confidence levels, Cisco warns 

**Upcoming events where you can find Talos **

**Botconf** **(April 23 - 26)** 

_Nice, Côte d'Azur, France_

> _This presentation from Chetan Raghuprasad details the Supershell C2 framework. Threat actors are using this framework massively and creating botnets with the Supershell implants._

**CARO Workshop 2024** **(May 1 - 3)** 

_Arlington, Virginia_

> Over the past year, we’ve observed a substantial uptick in attacks by YoroTrooper, a relatively nascent espionage-oriented threat actor operating against the Commonwealth of Independent Countries (CIS) since at least 2022. Asheer Malhotra's presentation at CARO 2024 will provide an overview of their various campaigns detailing the commodity and custom-built malware employed by the actor, their discovery and evolution in tactics. He will present a timeline of successful intrusions carried out by YoroTrooper targeting high-value individuals associated with CIS government agencies over the last two years.

**RSA** **(May 6 - 9)** 

_San Francisco, California_    

**Most prevalent malware files from Talos telemetry over the past week **

**SHA 256:** a31f222fc283227f5e7988d1ad9c0aecd66d58bb7b4d8518ae23e110308dbf91    
**MD5:** 7bdbd180c081fa63ca94f9c22c457376   
**Typical Filename:** c0dwjdi6a.dll |  
**Claimed Product:** N/A    
**Detection Name:** Trojan.GenericKD.33515991 

**SHA 256:** 744c5a6489370567fd8290f5ece7f2bff018f10d04ccf5b37b070e8ab99b3241  
**MD5:** a5e26a50bf48f2426b15b38e5894b189  
**Typical Filename:** a5e26a50bf48f2426b15b38e5894b189.vir  
**Claimed Product:** N/A  
**Detection Name:** Win.Dropper.Generic::1201

**SHA 256:** 3a2ea65faefdc64d83dd4c06ef617d6ac683f781c093008c8996277732d9bd66  
**MD5:** 8b84d61bf3ffec822e2daf4a3665308c  
**Typical Filename:** RemComSvc.exe  
**Claimed Product:** N/A   
**Detection Name:** W32.3A2EA65FAE-95.SBX.TG

**SHA 256:** 0e2263d4f239a5c39960ffa6b6b688faa7fc3075e130fe0d4599d5b95ef20647   
**MD5:** bbcf7a68f4164a9f5f5cb2d9f30d9790   
**Typical Filename:** bbcf7a68f4164a9f5f5cb2d9f30d9790.vir   
**Claimed Product:** N/A   
**Detection Name:** Win.Dropper.Scar::1201 

**SHA 256:** 62dfe27768e6293eb9218ba22a3acb528df71e4cc4625b95726cd421b716f983  
**MD5:** 0211073feb4ba88254f40a2e6611fcef  
**Typical Filename:** UIHost64.exe  
**Claimed Product:** McAfee WebAdvisor  
**Detection Name:** Trojan.GenericKD.68726899

There are plenty of ways to improve cybersecurity that don’t involve making workers return to a physical office

The thwarted XZ Utils supply chain attack was years in the making. Now, clues suggest nation-state hackers were behind the persona that inserted the malicious code.

Ultimately, Scott argues that those three years of code changes and polite emails were likely not spent sabotaging multiple software projects, but rather building up a history of credibility in preparation for the sabotage of XZ Utils specifically—and potentially other projects in the future. “He just never got to that step because we got lucky and found his stuff,” says Scott. “So that’s burned now, and he’s gonna have to go back to square one.”

**Technical Ticks and Time Zones**

Despite Jia Tan’s persona as a single individual, their yearslong preparation is a hallmark of a well-organized state-sponsored hacker group, argues Raiu, the former Kaspersky lead researcher. So too are the technical hallmarks of the XZ Utils malicious code that Jia Tan added. Raiu notes that, at a glance, the code truly looks like a compression tool. “It’s written in a very subversive manner,” he says. It’s also a “passive” backdoor, Raiu says, so it wouldn’t reach out to a command-and-control server that might help identify the backdoor’s operator. Instead, it waits for the operator to connect to the target machine via SSH and authenticate with a private key—one generated with a particularly strong cryptographic function known as ED448.

The backdoor’s careful design could be the work of US hackers, Raiu notes, but he suggests that’s unlikely, since the US wouldn’t typically sabotage open source projects—and if it did, the National Security Agency would probably use a quantum-resistant cryptographic function, which ED448 is not. That leaves non-US groups with a history of supply chain attacks, Raiu suggests, like China’s APT41, North Korea’s Lazarus Group, and Russia’s APT29.

At a glance, Jia Tan certainly looks East Asian—or is meant to. The time zone of Jia Tan’s commits are UTC+8: That’s China’s time zone, and only an hour off from North Korea’s. However, an analysis by two researchers, Rhea Karty and Simon Henniger, suggests that Jia Tan may have simply changed the time zone of their computer to UTC+8 before every commit. In fact, several commits were made with a computer set to an Eastern European or Middle Eastern time zone instead, perhaps when Jia Tan forgot to make the change.

“Another indication that they are not from China is the fact that they worked on notable Chinese holidays,” say Karty and Henniger, students at Dartmouth College and the Technical University of Munich, respectively. They note that Jia Tan also didn't submit new code on Christmas or New Year's. Boehs, the developer, adds that much of the work starts at 9 am and ends at 5 pm for Eastern European or Middle Eastern time zones. “The time range of commits suggests this was not some project that they did outside of work,” Boehs says.

Though that leaves countries like Iran and Israel as possibilities, the majority of clues lead back to Russia, and specifically Russia’s APT29 hacking group, argues Dave Aitel, a former NSA hacker and founder of the cybersecurity firm Immunity. Aitel points out that APT29—widely believed to work for Russia’s foreign intelligence agency, known as the SVR—has a reputation for technical care of a kind that few other hacker groups show. APT29 also carried out the Solar Winds compromise, perhaps the most deftly coordinated and effective software supply chain attack in history. That operation matches the style of the XZ Utils backdoor far more than the cruder supply chain attacks of APT41 or Lazarus, by comparison.

“It could very well be someone else,” says Aitel. “But I mean, if you’re looking for the most sophisticated supply chain attacks on the planet, that’s going to be our dear friends at the SVR.”

Security researchers agree, at least, that it’s unlikely that Jia Tan is a real person, or even one person working alone. Instead, it seems clear that the persona was the online embodiment of a new tactic from a new, well-organized organization—a tactic that nearly worked. That means we should expect to see Jia Tan return by other names: seemingly polite and enthusiastic contributors to open source projects, hiding a government’s secret intentions in their code commits.

_Updated 4/3/2024 at 12:30 pm ET to note the possibility of Israeli or Iranian involvement._

The Mystery of ‘Jia Tan,’ the XZ Backdoor Mastermind

Red Hat Security Advisory 2024-1601-03 - An update for curl is now available for Red Hat Enterprise Linux 8. Issues addressed include an information leakage vulnerability.

    The following advisory data is extracted from:https://access.redhat.com/security/data/csaf/v2/advisories/2024/rhsa-2024_1601.jsonRed Hat officially shut down their mailing list notifications October 10, 2023.  Due to this, Packet Storm has recreated the below data as a reference point to raise awareness.  It must be noted that due to an inability to easily track revision updates without crawling Red Hat's archive, these advisories are single notifications and we strongly suggest that you visit the Red Hat provided links to ensure you have the latest information available if the subject matter listed pertains to your environment.- Packet Storm Staff====================================================================Red Hat Security AdvisorySynopsis:           Moderate: curl security and bug fix updateAdvisory ID:        RHSA-2024:1601-03Product:            Red Hat Enterprise LinuxAdvisory URL:       https://access.redhat.com/errata/RHSA-2024:1601Issue date:         2024-04-02Revision:           03CVE Names:          CVE-2023-28322====================================================================Summary: An update for curl is now available for Red Hat Enterprise Linux 8.Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.Description:The curl packages provide the libcurl library and the curl utility for downloading files from servers using various protocols, including HTTP, FTP, and LDAP.Security Fix(es):* curl: information disclosure by exploiting a mixed case flaw (CVE-2023-46218)* curl: more POST-after-PUT confusion (CVE-2023-28322)* curl: cookie injection with none file (CVE-2023-38546)For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.Bug Fix(es):* libssh (curl sftp) not trying password auth (BZ#2240033)* libssh: cap SFTP packet size sent (RHEL-5485)Solution:https://access.redhat.com/articles/11258CVEs:CVE-2023-28322References:https://access.redhat.com/security/updates/classification/#moderatehttps://bugzilla.redhat.com/show_bug.cgi?id=2196793https://bugzilla.redhat.com/show_bug.cgi?id=2240033https://bugzilla.redhat.com/show_bug.cgi?id=2241938https://bugzilla.redhat.com/show_bug.cgi?id=2252030

Red Hat Security Advisory 2024-1601-03

Details are starting to emerge about a stunning supply chain attack that sent the open source software community reeling.

On Friday, a lone Microsoft developer rocked the world when he revealed a backdoor had been intentionally planted in XZ Utils, an open source data compression utility available on almost all installations of Linux and other Unix-like operating systems. The person or people behind this project likely spent years on it. They were likely very close to seeing the backdoor update merged into Debian and Red Hat, the two biggest distributions of Linux, when an eagle-eyed software developer spotted something fishy.

“This might be the best-executed supply chain attack we've seen described in the open, and it’s a nightmare scenario: malicious, competent, authorized upstream in a widely used library,” software and cryptography engineer Filippo Valsorda said of the effort, which came frightfully close to succeeding.

Researchers have spent the weekend gathering clues. Here’s what we know so far.

**What Is XZ Utils?**

XZ Utils is nearly ubiquitous in Linux. It provides lossless data compression on virtually all Unix-like operating systems, including Linux. XZ Utils provides critical functions for compressing and decompressing data during all kinds of operations. XZ Utils also supports the legacy .lzma format, making this component even more crucial.

**What Happened?**

Andres Freund, a developer and engineer working on Microsoft’s PostgreSQL offerings, was recently troubleshooting performance problems a Debian system was experiencing with SSH, the most widely used protocol for remotely logging in to devices over the Internet. Specifically, SSH logins were consuming too many CPU cycles and were generating errors with valgrind, a utility for monitoring computer memory.

Through sheer luck and Freund’s careful eye, he eventually discovered the problems were the result of updates that had been made to XZ Utils. On Friday, Freund took to the Open Source Security List to disclose the updates were the result of someone intentionally planting a backdoor in the compression software.

**What Does the Backdoor Do?**

Malicious code added to XZ Utils versions 5.6.0 and 5.6.1 modified the way the software functions when performing operations related to .lzma compression or decompression. When these functions involved SSH, they allowed for malicious code to be executed with root privileges. This code allowed someone in possession of a predetermined encryption key to log in to the backdoored system over SSH. From then on, that person would have the same level of control as any authorized administrator.

**How Did This Backdoor Come to Be?**

It would appear that this backdoor was years in the making. In 2021, someone with the username JiaT75 made their first known commit to an open source project. In retrospect, the change to the libarchive project is suspicious, because it replaced the safe\_fprint funcion with a variant that has long been recognized as less secure. No one noticed at the time.

The following year, JiaT75 submitted a patch over the XZ Utils mailing list, and, almost immediately, a never-before-seen participant named Jigar Kumar joined the discussion and argued that Lasse Collin, the longtime maintainer of XZ Utils, hadn’t been updating the software often or fast enough. Kumar, with the support of Dennis Ens and several other people who had never had a presence on the list, pressured Collin to bring on an additional developer to maintain the project.

In January 2023, JiaT75 made their first commit to XZ Utils. In the months following, JiaT75, who used the name Jia Tan, became increasingly involved in XZ Utils affairs. For instance, Tan replaced Collins’ contact information with their own on oss-fuzz, a project that scans open source software for vulnerabilities that can be exploited. Tan also requested that oss-fuzz disable the ifunc function during testing, a change that prevented it from detecting the malicious changes Tan would soon make to XZ Utils.

In February of this year, Tan issued commits for versions 5.6.0 and 5.6.1 of XZ Utils. The updates implemented the backdoor. In the following weeks, Tan or others appealed to developers of Ubuntu, Red Hat, and Debian to merge the updates into their OSes. Eventually, one of the two updates made its way into several releases, according to security firm Tenable. There’s more about Tan and the timeline here.

**Can You Say More About What This Backdoor Does?**

In a nutshell, it allows someone with the right private key to hijack sshd, the executable file responsible for making SSH connections, and from there to execute malicious commands. The backdoor is implemented through a five-stage loader that uses a series of simple but clever techniques to hide itself. It also provides the means for new payloads to be delivered without major changes being required.

Multiple people who have reverse-engineered the updates have much more to say about the backdoor. Developer Sam James provided an overview here.

The XZ Backdoor: Everything You Need to Know

By Waqas
Critical Backdoor Alert! Patch XZ Utils Now (CVE-2024-3094) & Secure Your Linux System. Learn how a hidden backdoor…
This is a post from HackRead.com Read the original post: Backdoor Discovered in XZ Utils: Patch Your Systems Now (CVE-2024-3094)

Critical Backdoor Alert! Patch XZ Utils Now (CVE-2024-3094) & Secure Your Linux System. Learn how a hidden backdoor puts Linux at risk and how to patch it immediately.

A critical security vulnerability, designated CVE-2024-3094, was recently discovered in the widely used XZ Utils package. This vulnerability threatens Linux systems with backdoor attacks.

For your information, XZ Utils is a collection of open-source command-line tools for data compression and decompression. It includes the popular xz command and the liblzma library, which is used by other software, most notably OpenSSH – the program that enables secure remote access to Linux systems.

****The Backdoor Explained****

The vulnerability involved a malicious backdoor hidden within the source code of XZ Utils, specifically in the liblzma library. This backdoor code, if triggered, could allow an attacker to gain unauthorized remote access to a vulnerable system through SSH. The attacker wouldn’t even need valid credentials, potentially granting complete control over the system.

****Impact and Discovery****

The potential impact of this vulnerability is severe. An attacker exploiting CVE-2024-3094 could steal sensitive data, install malware, disrupt critical operations, or even use the compromised system to launch further attacks.

Fortunately, the backdoor was discovered by the security community in late March 2024 before widespread distribution. This prevented a large-scale security breach. However, some Linux users remain vulnerable, especially those using unstable or rolling-release distributions.

****Who is Affected?****

According to OpenSSH’s report, the specific versions of XZ Utils containing the backdoor were 5.6.0 and 5.6.1. These versions were only recently released and did not make it into the stable branches of most major Linux distributions. However, users who manually compiled these versions from source code or installed them from non-standard repositories could be at risk.

Commenting on this, John Bambenek, President at Bambenek Consulting warned, _“_The original reports of this backdoor showed exploitation of this vulnerability via SSH which means it can be triggered even if the victim machine’s users don’t use XZ and its library. It seems this library tends to be installed by default on modern Linux distributions so organizations should immediately prioritize downgrading the package until a safe update is released, even if they don’t use the tools themselves._“_

****Mitigation and Prevention****

The most critical step to address this vulnerability is to update your system immediately. Most Linux distributions have released patch updates for XZ Utils. Here’s how to update depending on your distribution:

*   **Debian/Ubuntu:** Use sudo apt update and sudo apt upgrade commands.
*   **Red Hat/CentOS/Fedora:** Use sudo dnf update command.
*   **Other Distributions:** Refer to your distribution’s specific update instructions.

****Lessons Learned****

The discovery of CVE-2024-3094 emphasizes the importance of various security measures. Firstly, keeping software and systems updated with regular patches is crucial to mitigate potential risks.

Secondly, maintaining a sharp review process for open-source projects aids in the early detection of vulnerabilities. Thirdly, promoting security awareness among users and employees through education about risks and best practices is essential for enhancing overall protection. Adhering to these practices enables us to reduce the impact of vulnerabilities like CVE-2024-3094 and safeguard the security of our systems.

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Backdoor Discovered in XZ Utils: Patch Your Systems Now (CVE-2024-3094)

Had a Microsoft developer not spotted the malware when he did, the outcome could have been much worse.

Source: ozrimoz via Shutterstock

A newly discovered backdoor in XZ Utils, a data compression utility present in nearly all Linux distributions, has revived the ghosts of previous major software-supply chain security scares such as the Log4Shell vulnerability and the attack on SolarWinds.

The backdoor is embedded in an XZ library called liblzma and gives remote attackers a way to bypass secure shell (sshd) authentication and then gain complete access to an affected system. An individual with maintainer-level access to the code appears to have deliberately introduced the backdoor in a painstakingly executed, multiyear attack.

**A Shock to the OSS Community**

The backdoor affects XZ Utils 5.6.0 and 5.6.1, which are versions of the utility currently used only in unstable and beta releases of Fedora, Debian, Kali, open SUSE, and Arch Linux. As a result, the potential threat with this backdoor for now is considerably more limited than if the malware had found its way into a stable Linux distro.

Even so, the fact that someone managed to sneak a nearly undetectable backdoor into a trusted, widely used open source component — and the potential havoc it could have caused — has come as a painful wakeup call on how vulnerable organizations remain to attacks via the supply chain.

"This supply chain attack came as a shock to the OSS community, as XZ Utils was considered a trusted and scrutinized project," JFrog researchers said in a blog post. "The attacker built up a credible reputation as an OSS developer over the span of multiple years and used highly obfuscated code in order to evade detection by code reviews."

XZ Util is a command-line utility for compressing and decompressing data in Linux and other Unix-like operating systems. Microsoft developer Andres Freund discovered the backdoor in the software when investigating odd behavior in recent weeks around liblzma on some Debian installations. After initially thinking the backdoor was purely a Debian problem, Freund discovered the issue actually impacted the upstream XZ repository and associated tarballs or archive files. He publicly disclosed the threat on March 29.

Over the weekend, security teams associated with Fedora, Debian, openSUSE, Kali, and Arch issued urgent advisories alerting organizations running the affected Linux releases to immediately revert to earlier, more stable releases of their software to mitigate the potential risk of remote-code execution.

**Maximum Severity Vuln**

Red Hat, the primary sponsor and contributor to Fedora, assigned the backdoor a vulnerability identifier (CVE-2024-3094) and assessed it as a maximum severity risk (CVSS score of 10) to draw attention to the threat. The US Cybersecurity and Infrastructure Security Agency (CISA) joined the chorus of voices urging organizations using affected Linux distributions to downgrade their XZ Utils to an earlier version, and to hunt for any potential activity related to the backdoor and report any such findings to the agency.

All of the advisories offered tips for users on how to quickly check for the presence of the back-doored XZ versions in their code. Red Hat released an update that reverts XZ to previous versions, which the company will make available via its normal update process. But users concerned about potential attacks can force the update if they don't want to wait for the update to become available via the normal process, the company said.

Today Binarly released a free tool that organizations can use to look for backdoored XZs as well.

"Had this malicious code been introduced to stable OS releases in multiple Linux distributions, we could have seen in-the-wild exploitation en-masse," says Scott Caveza, staff research engineer at Tenable. "The longer this went unnoticed, the greater the potential for more malicious code from whomever this malicious actor might be."

In an FAQ, Tenable described the backdoor as modifying functions within liblzma in such a way as to allow attackers to intercept and modify data within the library. "In the example observed by Freund, under certain conditions, this backdoor could allow a malicious actor to 'break sshd authentication,' allowing the attacker to gain access to an affected system," noted the researchers.

**XZ Utils "Maintainer" Behind the Backdoor**

What makes the backdoor especially troublesome is the fact that someone using an account belonging to a maintainer of XZ Util embedded the malware in the package in what appears to have been a carefully planned multiyear operation. In a widely referenced blog post, security researcher Evan Boehs traced the malicious activity back to 2021 when an individual using the name Jia Tan created a GitHub account and almost immediately started making suspicious changes to some open source projects.

The blog post provides a detailed timeline of the steps Jia Tan and a couple of other individuals took to gradually build enough trust within the XZ community to make changes to the software and eventually introduce the backdoor.

"All the evidence points to social manipulation being used by a person with the sole end goal of inserting a backdoor," Boehs tells Dark Reading. "Basically, there was never a genuine effort to maintain the project, only to gain enough trust to insert \[the backdoor\] quietly."

Typically, gaining commit access to a repository requires an individual to establish a sense of trustworthiness. Often, projects give new commit access to individuals only when there is a need for it and after some risk assessment, Boehs says.

"In this case, Jia created a \[seemingly\] legitimate need for more maintainers ... and then began building trust. Our society is built on trust, and occasionally some crafty people exploit it," he notes. "Gaining permission requires trust. Trust takes time to establish. Jia was in it for the long game."

Boehs says it's unclear when exactly Jia Tan became a trusted member of the repository. But soon after his first commit in 2022, Jia Tan became a regular contributor and is currently the second-most active on the project. GitHub has since suspended Jia Tan's account.

Saumitra Das, vice president of engineering at Qualys, says what happened with XZ Util can happen elsewhere.

"Many critical libraries in open source are being maintained by volunteers in the community who are not paid for it and can be under pressure due to their personal issues," Das says.

Maintainers who are under pressure often welcome contributors who are willing to spend even a little bit of time on their projects. "Over, time, such folks can gain more control over the code," as was the case with XZ Utils, he says.

**About the Author(s)**

Jai Vijayan is a seasoned technology reporter with over 20 years of experience in IT trade journalism. He was most recently a Senior Editor at Computerworld, where he covered information security and data privacy issues for the publication. Over the course of his 20-year career at Computerworld, Jai also covered a variety of other technology topics, including big data, Hadoop, Internet of Things, e-voting, and data analytics. Prior to Computerworld, Jai covered technology issues for The Economic Times in Bangalore, India. Jai has a Master's degree in Statistics and lives in Naperville, Ill.

XZ Utils Backdoor Implanted in Carefully Executed, Multiyear Supply Chain Attack

Debian Linux Security Advisory 5651-1 - Two security issues were discovered in MediaWiki, a website engine for collaborative work, which could result in cross-site scripting or denial of service.

    -----BEGIN PGP SIGNED MESSAGE-----Hash: SHA512- -------------------------------------------------------------------------Debian Security Advisory DSA-5651-1                   security@debian.orghttps://www.debian.org/security/                       Moritz MuehlenhoffMarch 31, 2024                        https://www.debian.org/security/faq- -------------------------------------------------------------------------Package        : mediawikiCVE ID         : not yet availableTwo security issues were discovered in MediaWiki, a website engine forcollaborative work, which could result in cross-site scripting or denialof service.For the oldstable distribution (bullseye), this problem has been fixedin version 1:1.35.13-1+deb11u2.For the stable distribution (bookworm), this problem has been fixed inversion 1:1.39.7-1~deb12u1.We recommend that you upgrade your mediawiki packages.For the detailed security status of mediawiki please refer toits security tracker page at:https://security-tracker.debian.org/tracker/mediawikiFurther information about Debian Security Advisories, how to applythese updates to your system and frequently asked questions can befound at: https://www.debian.org/security/Mailing list: debian-security-announce@lists.debian.org-----BEGIN PGP SIGNATURE-----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YhNf-----END PGP SIGNATURE-----

Debian Security Advisory 5651-1

Gentoo Linux Security Advisory 202403-4 - A backdoor has been discovered in XZ utils that could lead to remote compromise of systems. Versions less than 5.6.0 are affected.

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Gentoo Linux Security Advisory                           GLSA 202403-04  
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                                           https://security.gentoo.org/  
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 Severity: High  
    Title: XZ utils: Backdoor in release tarballs  
     Date: March 29, 2024  
     Bugs: #928134  
       ID: 202403-04

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Synopsis  
========

A backdoor has been discovered in XZ utils that could lead to remote  
compromise of systems.

Background  
==========

XZ Utils is free general-purpose data compression software with a high  
compression ratio.

Affected packages  
=================

Package            Vulnerable    Unaffected  
-----------------  ------------  ------------  
app-arch/xz-utils  >= 5.6.0      < 5.6.0

Description  
===========

A backdoor has been discovered in XZ utils. Please review the CVE  
identifier referenced below for details.

Impact  
======

Our current understanding of the backdoor is that is does not affect  
Gentoo systems, because

1. the backdoor only appears to be included on specific systems and  
Gentoo does not qualify;  
2. the backdoor as it is currently understood targets OpenSSH patched to  
work with systemd-notify support. Gentoo does not support or include  
these patches;

Analysis is still ongoing, however, and additional vectors may still be  
identified. For this reason we are still issuing this advisory as if  
that will be the case.

Workaround  
==========

There is no known workaround at this time.

Resolution  
==========

All XZ utils users should downgrade to the latest version before the  
backdoor was introduced:

  # emerge --sync  
  # emerge --ask --oneshot --verbose "<app-arch/xz-utils-5.6.0"

References  
==========

[ 1 ] CVE-2024-3094  
      https://nvd.nist.gov/vuln/detail/CVE-2024-3094

Availability  
============

This GLSA and any updates to it are available for viewing at  
the Gentoo Security Website:

 https://security.gentoo.org/glsa/202403-04

Concerns?  
=========

Security is a primary focus of Gentoo Linux and ensuring the  
confidentiality and security of our users' machines is of utmost  
importance to us. Any security concerns should be addressed to  
security@gentoo.org or alternatively, you may file a bug at  
https://bugs.gentoo.org.

License  
=======

Copyright 2024 Gentoo Foundation, Inc; referenced text  
belongs to its owner(s).

The contents of this document are licensed under the  
Creative Commons - Attribution / Share Alike license.

https://creativecommons.org/licenses/by-sa/2.5

Gentoo Linux Security Advisory 202403-04

Security vulnerabilities discovered in Dormakaba's Saflok electronic RFID locks used in hotels could be weaponized by threat actors to forge keycards and stealthily slip into locked rooms.
The shortcomings have been collectively named Unsaflok by researchers Lennert Wouters, Ian Carroll, rqu, BusesCanFly, Sam Curry, sshell, and Will Caruana. They were reported to the Zurich-based

Dormakaba Locks Used in Millions of Hotel Rooms Could Be Cracked in Seconds

Updated March 30, 2024: We have determined that Fedora Linux 40 beta does contain two affected versions of xz libraries - xz-libs-5.6.0-1.fc40.x86_64.rpm and xz-libs-5.6.0-2.fc40.x86_64.rpm. At this time, Fedora 40 Linux does not appear to be affected by the actual malware exploit, but we encourage all Fedora 40 Linux beta users to revert to 5.4.x versions.Editor's note: This post has been updated to more clearly articulate the affected versions of Fedora Linux and add additional mitigation methods.Yesterday, Red Hat Information Risk and Security and Red Hat Product Security learned that the l

_Updated March 30, 2024: We have determined that Fedora Linux 40 beta does contain two affected versions of xz libraries - xz-libs-5.6.0-1.fc40.x86\_64.rpm and xz-libs-5.6.0-2.fc40.x86\_64.rpm. At this time, Fedora 40 Linux does not appear to be affected by the actual malware exploit, but we encourage all Fedora 40 Linux beta users to revert to 5.4.x versions._

_Editor's note: This post has been updated to more clearly articulate the affected versions of Fedora Linux and add additional mitigation methods._

Yesterday, Red Hat Information Risk and Security and Red Hat Product Security learned that the latest versions of the “xz” tools and libraries **contain** **malicious code** **that appears to be intended to allow unauthorized access. Specifically, this code is present in versions 5.6.0 and 5.6.1 of the libraries**. Fedora Linux 40 users may have received version 5.6.0, depending on the timing of system updates. Fedora Rawhide users may have received version 5.6.0 or 5.6.1. This vulnerability was assigned CVE-2024-3094.

**PLEASE IMMEDIATELY STOP USAGE OF ANY FEDORA RAWHIDE INSTANCES** for work or personal activity. Fedora Rawhide will be reverted to xz-5.4.x shortly, and once that is done, Fedora Rawhide instances can safely be redeployed. _Note that Fedora Rawhide is the development distribution of Fedora Linux, and serves as the basis for future Fedora Linux builds (in this case, the yet-to-be-released Fedora Linux 41)._

**At this time the Fedora Linux 40 builds have not been shown to be compromised.** We believe the malicious code injection did not take effect in these builds. However, Fedora Linux 40 users should still downgrade to a 5.4 build to be safe. An update that reverts xz to 5.4.x has recently been published and is becoming available to Fedora Linux 40 users through the normal update system. Concerned users can force the update by following the instructions at https://bodhi.fedoraproject.org/updates/FEDORA-2024-d02c7bb266.

_Updated March 30, 2024: We have determined that Fedora Linux 40 beta does contain two affected versions of xz libraries - xz-libs-5.6.0-1.fc40.x86\_64.rpm and xz-libs-5.6.0-2.fc40.x86\_64.rpm. At this time, Fedora 40 Linux does not appear to be affected by the actual malware exploit, but we encourage all Fedora 40 Linux beta users to revert to 5.4.x versions._

**What is xz?**

xz is a general purpose data compression format present in nearly every Linux distribution, both community projects and commercial product distributions. Essentially, it helps compress (and then decompress) large file formats into smaller, more manageable sizes for sharing via file transfers.

**What is the malicious code?**

The malicious injection present in the xz versions 5.6.0 and 5.6.1 libraries is obfuscated and only included in full in the download package - the Git distribution lacks the M4 macro that triggers the build of the malicious code. The second-stage artifacts are present in the Git repository for the injection during the build time, in case the malicious M4 macro is present.

The resulting malicious build interferes with authentication in sshd via systemd.  SSH is a commonly used protocol for connecting remotely to systems, and sshd is the service that allows access.  **Under the right circumstances this interference could potentially enable a malicious actor to break sshd authentication and gain unauthorized access to the entire system remotely.**

**What distributions are affected by this malicious code?**

Current investigation indicates that the packages are only present in Fedora 40 and Fedora Rawhide within the Red Hat community ecosystem.

_**No versions of Red Hat Enterprise Linux (RHEL) are affected.**_

We have reports and evidence of the injections successfully building in xz 5.6.x versions built for Debian unstable (Sid). Other distributions may also be affected. Users of other distributions should consult with their distributors for guidance.

**What should I do if I am running an affected distribution?**

For both personal and business activities, immediately stop using Fedora 40 or Fedora Rawhide until you can downgrade your xz version. If you are using an affected distribution in a business setting, we encourage you to contact your information security team for next steps.

Additionally, for those running openSUSE distributions, SUSE has published a downgrade procedure at https://build.opensuse.org/request/show/1163302.

Tag

#ssh