Patch Tuesday turned security updates from chaotic events into a routine. Here's how we got here and where things might be heading.

On Oct. 9, 2003, Microsoft CEO Steve Ballmer announced that the company would issue security patches only once a month to "reduce the burden on IT administrators by adding a level of increased predictability and manageability."

Two decades later, Microsoft continues to issue its security updates on the second Tuesday of every month, with occasional exceptions for emergency situations. Many other companies, like Oracle and Adobe, follow similar rules.

Patch Tuesday turned risk management into a monthly appointment, but like many innovations it was founded from crisis. At the beginning of 2002, shortly after the world experienced two of its first cyber doomsdays, Code Red and Nimda, Microsoft decided to change its philosophy around security. The two worms, which infected hundreds of thousands of machines in a matter of hours, exploited vulnerabilities for which patches were available.

"The problem was not that we weren't building patches; the problem was that people weren't deploying them quickly enough," says Christopher Budd, who was with Microsoft from 2000 to 2010 and is now a senior manager for threat research at Sophos.

At that time, the trauma of 9/11 was palpable in North America, and there was a growing concern within Microsoft regarding security. On Jan. 15, 2002, Bill Gates sent his famous Trustworthy Computing memo, highlighting the importance of protecting customers and their systems.

One way to improve security was to change how patches were delivered. So instead of announcing them unpredictably, on a ship-when-ready basis, several times during a week, Microsoft began to stack them together to make it easier for customers to keep up.

At first, the idea was implemented as a "silent pilot project," Budd says. But as it showed promising results, it was soon made official. The first official Patch Tuesday report was published on Oct. 14, 2003, and it included seven vulnerabilities, five of which were seen as critical.

"Tuesday was the earliest day in the week that we felt we could sustainably offer these," says Budd, who helped build Patch Tuesday.

This fixed-schedule approach has become a standard industry practice. But the road was not always smooth.

**The Early Days of Patch Tuesday**

Throughout the years, Microsoft has evolved and refined its approach to security patches, adapting to changing threats. Notable worms that followed Code Red, such as Sasser and Blaster, helped Patch Tuesday to grow and eventually mature.

Budd and his colleagues in the Microsoft Security Response Center, who "suddenly became incredibly important" after the Trustworthy Computing memo, tried to make improvements around patch deployment and detection. One key achievement was to build tools that enabled admins to do a scan and identify the systems that needed security updates — an idea that, while simple, proved to be a game-changer.

The entire process of releasing patches required extensive work, particularly on the Monday before Patch Tuesday, when everything had to be checked. Security experts put in long hours, missed birthday parties, and even showered in Microsoft's headquarters because they didn't have the time to go home.

It is why the releases of the bulletins were celebrated with music blasting over loudspeakers. "When the bulletins were live, it was a big deal for us," says Dustin Childs, who was with Microsoft between 2008 to 2014 and is now the head of threat awareness at Trend Micro's Zero Day Initiative.

Typically, the music was picked by the release manager for that bulletin. "I remember one month it was Klingon music, but it was usually rock and roll," Childs says.

Occasionally, soon after the music stopped, chaos would ensue because some patches caused unintended consequences. One notable incident happened in February 2010, when thousands of customers reported blue screens almost immediately.

When security experts in Redmond heard about the issue, they tried to replicate it but were unsuccessful. For the lack of a better solution, Microsoft bought the computer of a customer who called a support center near Dallas to report the issue.

"And as soon as we got that computer, we found that it had a rootkit installed in it," Childs says.

The Alureon rootkit made modifications to Windows Kernel binaries, which caused the systems to be unstable. The company reissued the patch and fixed the problem.

"The really funny part, though, was that the people who made the rootkit figured it out faster than we did, and they had updated their rootkit to avoid the patch within 48 hours \[of the release\]," Childs says. "It took us a week to fix it!"

And it wasn't the only bizarre episode in Patch Tuesday's history. For instance, Childs remembers that an Internet Explorer patch crashed online banking in South Korea, while a Windows Media Player patch broke an entire country — twice.

"For some reason, on systems in Denmark, it blue-screened," he says. "So we had to recall that patch, fix it and re-release it. And then, the very next month, the same thing happened again. I don't know what was specific about the systems in Denmark."

Even today, some patches released by software companies in general, not just Microsoft, can cause issues, which can be frustrating for those installing them. Childs argues that if vendors improve the reliability of these fixes, customers might be more willing to apply them promptly, as opposed to waiting weeks or months to see if others experienced issues.

Taking the waiting approach can be risky, as it leaves their systems vulnerable to known vulnerabilities. It is why Childs recommends users apply patches as soon as possible. He also tells them to call attention to poor-quality patches.

"Let's hold vendors accountable," Childs says. "Let's make sure that they're producing good patches."

Aanchal Gupta, deputy CISO at Microsoft, says the company is doing "extensive testing" of patches.

"Before we issue any patch to our customers, it goes through rigorous testing not just within Microsoft. ... \[W\]e also have a set of beta testers, external companies, and they get the patches early on before these are actually made public," she says. "They can test in their environment and report back to us whether there is something unique in their environment which could make the patch not work."

**Patch Tuesday Today**

Patch Tuesday has come a long way since those early days when Klingon music blasted from the speakers. Over time, the releases have become quieter and even automated, becoming invisible to some users.

In the past decade, Microsoft has made several changes to streamline the process. In the mid-2010s, for instance, it announced cumulative updates so that a customer who missed, for instance, five patches only needed to apply the last one because the other ones were included in it. The company also launched machine-readable Security Update Guides, which meant that organizations with huge fleet deployments could rely on automation.

But not every change was welcomed by the community. When Microsoft decided to eliminate security bulletins and replace them with Security Update Guides, customers complained that the information they received was less intuitive. Something similar happened in the fall of 2020, when the tech giant removed executive summaries that included detailed information on vulnerabilities. Once again, many in the industry argued that they didn't receive enough information, which made their decision-making processes difficult.

That was "probably the most disruptive" decision Microsoft made, says security researcher Claire Tills. "I know some defenders also really had trouble with that."

More recently, in 2022 Microsoft took yet another step toward making Patch Tuesday a regular Tuesday, when it announced Autopatch, which promised to ease the process of addressing vulns for customers with Windows Enterprise E3 and E5 licenses. The move made organizations wonder whether Patch Tuesday as we know it might disappear — a rumor Microsoft denied.

The publicity around Patch Tuesday is getting smaller and the number of Patch Tuesday vulnerabilities may have peaked. In 2020, a particularly "aggressive year," Tills counted around 1,200 vulns, while in 2022, she saw 663.

"In terms of the types of vulnerabilities, it's consistently elevation of privilege and remote code execution," she says. "Every once in a while, we'll get peaks in information disclosures and security feature bypass — those two also pop up."

But despite the features meant to streamline the process of applying patches, this task can still be daunting for small businesses that can't afford a dedicated tech support team. It is why Gupta recommends these clients to move to the cloud.

"Then you can purely focus on your business and you don't have to worry about patching and managing systems," she says. "I also encourage people to not disable the default upgrades."

But as we transition toward automating the processes, is dedicating one day for updates obsolete?

**Is Patch Tuesday Becoming Obsolete?**

It is hard to fathom a world of cybersecurity without Patch Tuesday, which has been an integral part of the industry for two decades. As threats become more sophisticated and geopolitics becomes more volatile, however, the traditional model of Patch Tuesday may no longer be sufficient to keep systems secure.

Organizations operating in complex environments, such as in those competitive fields or based in hot areas like Ukraine, cannot afford to make mistakes when it comes to patch management. Threat actors often "targeted technical vulnerabilities rather than specific individuals or organizations," says Nazar Tymoshyk, founder and CEO of cybersecurity startup UnderDefense, which has protected several organizations during the ongoing war with Russia.

"The exploitation of unpatched vulnerabilities in technology stacks or outdated Web resources still accounts for 50% of \[Russia's\] success in cyber-intelligence operations," he says.

Tymoshyk believes that Patch Tuesday is still necessary and should not be retired. However, organizations should build on top of it, adopting additional patching routines depending on the size and complexity of their infrastructure or the types of software and systems they use.

Satnam Narang, senior staff research engineer at Tenable, also favors keeping Patch Tuesday alive because routines can help organizations foster a security-focused culture.

"Each week the folks come to pick up the trash from our street, and we know that that's happening every week on a specific day," he says. "The reason why Patch Tuesday is a valuable resource is that it happens every month on a specific day, so it allows organizations to carve out the time necessary to patch these vulnerabilities."

A chaotic patching system might not work, Narang says, because security teams are already overwhelmed. Aviv Grafi, CTO and founder at Votiro, agrees. "Time is of the essence, and we need to focus on leveraging technologies and software that give security teams more time back in their day," Grafi says.

Security researchers also add that continual patch cycles and automatic updates might not always be feasible at enterprise level in some cases. "In the event of a problem, large organizations need to be able to revert systems to a known state, and that requires planning," says David Farquhar, solutions architect at Nucleus.

Patch Tuesday is a crucial element in the routines of many organizations, but despite that, it can be unpredictable. The past years have shown that its structure can change without prior warnings. "Even though Patch Tuesday feels so foundational and so solid, it can change at the drop of a hat," Tills says. "The end of Patch Tuesday could feel disastrous for a lot of organizations."

For the time being, though, it appears that Microsoft will keep the program running. "I wouldn't worry about Patch Tuesday going away anytime soon," Gupta says.

How Patch Tuesday Keeps the Beat After 20 Years

Security vendors urge organizations to fix the actively exploited bugs, in Microsoft Outlook and the Mark of the Web feature, immediately.

IT teams should prioritize the patching of two zero-day vulnerabilities, one in Microsoft Outlook's authentication mechanism and another that's a Mark of the Web bypass, security experts said today. The two are part of a cache of 74 security bugs that Microsoft disclosed in its March Patch Tuesday security update.

In a blog post, researchers from Automox recommended that organizations patch both vulnerabilities within 24 hours since attackers are exploiting them in the wild. 

In addition, several of the critical flaws in the March update enable remote code execution (RCE), making them a high priority for patching as well. 

Vendors had slightly different takes on the total number of new critical vulnerabilities in Microsoft's March update — likely because of differences in what they included in the count. Trend Micro's Zero-Day Initiative (ZDI), for instance, identified six of the vulnerabilities in Microsoft's March update as critical, while Tenable and Action1 pegged the number at nine.

**Privilege Escalation Zero-Day**

One of the zero-days is a critical privilege escalation vulnerability in Microsoft Outlook tracked as CVE-2023-23397, which allows an attacker to access the victim's Net-NTLMv2 challenge-response authentication hash and then impersonate the user. 

What makes the bug dangerous is that an attacker could trigger it simply by sending a specially crafted email that Outlook retrieves and processes before the user even views it in the Preview Pane.

"This is because the vulnerability is triggered on the email server side, meaning exploitation would occur before a victim views the malicious email," said Satnam Narang, senior staff research engineer at Tenable in an emailed comment. An attacker could use the victim's Net-NLMv2 hash to conduct an attack that exploits the NTLM challenge-response mechanism and allows the adversary to authenticate as the user.

That makes the bug more of an authentication bypass vulnerability than an privilege escalation issue, added ZDI researcher Dustin Childs, in a blog post that summarized the most important flaws in Microsoft's March Patch Tuesday update. Disabling the Preview Pane option will not mitigate the threat because the bug gets triggered even before that, he wrote.

Microsoft attributed the bug's discovery to researchers from Ukraine's Computer Emergency Response Team (CERT) as well as one of its own researchers.

Organizations that cannot patch CVE-2023-23397 immediately should consider implementing Microsoft's mitigation for the flaw, which prevents the use of NTLM as an authentication mechanism, Automox said.

**Actively Exploited Security Feature Bypass Flaw**

Microsoft identified the second zero-day bug as CVE-2023-24880, a Windows SmartScreen security feature bypass issue than at attacker could use to bypass the Mark of the Web designation that Microsoft uses to identify files that a user might download from the Internet. 

The feature is designed to warn users about potentially unsafe content. CVE-2023-24880 affects all desktop systems running Windows 10 and above and systems running Windows Server 2016, 2019, and 2022.

Chris Goettl, vice president of security products at Ivanti, cautioned administrators not to be lulled into a sense of false security by Microsoft's relatively low severity rating for the flaw. 

"The CVSSv3.1 score is only 5.4, which may avoid notice by many organizations," Goettl said in a statement. On its own, the CVE may not be all that threatening, "but it was likely used in an attack chain with additional exploits," he warned.

**Other Security Bugs at High Patching Priority**

One of the RCE flaws to make a special note of is CVE-2023-23415, which exists in the Internet Control Message Protocol (ICMP) that network devices use to diagnose communications issues. 

"An attacker can remotely exploit this vulnerability through the use of a low-level protocol error containing a fragmented IP packet in its header that is sent to the target machine," Microsoft said. The vulnerability affects multiple Microsoft products, including Windows 10, Windows 11, Windows Server 2008, 2012, 2016, 2019, and 2022.

ZDI, Automox, and Action1 also all identified a RCE vulnerability with a near maximum severity of 9.8 on the CVSS scale in the HTTP Protocol Stack as another issue that organizations might want to prioritize. 

The vulnerability (CVE-2023-23392) allows an unauthenticated attacker to send a specially crafted packet to a server that uses the HTTP Protocol Stack leading to RCE. "The vulnerability affects Windows Server 2022 and Windows 11, and has a low-complexity attack vector that requires no privileges or user interaction," Action1 warned. Because of this, Microsoft has assessed the vulnerability as one that threat actors are more likely to exploit than other flaws.

Automox also recommended that organizations address CVE-2023-23416, a RCE bug in the Windows Cryptographic Services protocol, within 72 hours. That's because, among other things, it affects all versions of desktops Windows 10 and above, and all Windows server editions from Server 2012 on.

In addition to patches for new vulnerabilities, Microsoft also issued updates for four older flaws — all from 2022 — in its March patch cycle. The update expands the number of Microsoft software and applications affected by the vulnerabilities and provides a patch for them, Ivanti said. The security vendor identified the four updated patches as CVE-2022-43552, CVE-2022-23257, CVE-2022-23825, and CVE-2022-23816.

Microsoft Zero-Day Bugs Allow Security Feature Bypass

Microsoft disclosed 83 vulnerabilities across the company’s hardware and software line, including two issues that are actively being exploited in the wild, continuing a trend of zero-days appearing in Patch Tuesdays over the past few months.

Tuesday, March 14, 2023 16:03

Microsoft released its monthly security update Tuesday, disclosing 83 vulnerabilities across the company’s hardware and software line, including two issues that are actively being exploited in the wild, continuing a trend of zero-days appearing in Patch Tuesdays over the past few months.

Two of the vulnerabilities included in March’s security update have been exploited in the wild, according to Microsoft, including one critical issue.

In all, eight of the issues disclosed this month are critical, while the remainder — outside of one — is “important.”

A moderate-severity vulnerability that’s already being exploited in the wild is CVE-2023-24880, a security feature bypass vulnerability in Windows SmartScreen, a cloud-based anti-phishing and anti-malware feature included in several Microsoft products. An attacker could exploit this vulnerability to craft a malicious file that would evade Mark of the Web (MOTW) defenses, resulting in a limited loss of integrity and availability of security features such as Protected View in Microsoft Office, which rely on MOTW tagging. This, in theory, could allow the attacker to pass a malicious file through without it being detected.

The other zero-day included this month is CVE-2023-23397, a privilege escalation vulnerability in Microsoft Outlook that could force a targeted device to connect to a remote URL and transmit the Windows account's Net-NTLMv2 hash to an adversary.

To trigger this vulnerability, a user doesn’t even need to open the email or preview it, the vulnerability is triggered as soon as the email is retrieved by the targeted email server.

Three of the other critical vulnerabilities Microsoft is patching have a CVSS severity score of 9.8 out of 10: CVE-2023-21708, CVE-2023-23392 and CVE-2023-23415.

CVE-2023-21708 is a remote code execution vulnerability in Microsoft Remote Call Procedure (RCP). To exploit this vulnerability, an unauthenticated attacker could send a specially crafted RPC call to an RPC host. This could result in remote code execution on the server side with the same permissions as the RPC service.

The attacker would need to have access to TCP port 135 on the remote host, so Microsoft considers this vulnerability “less likely” to be exploited, especially from an outside network perimeter. But an attacker who already have a foothold on an internal network could use this vulnerability to compromise other machines in the same domain if the target doesn’t block this port.

Another remote code execution vulnerability exists on the HTTP protocol stack on Windows 11 and Windows Server 2022. An attacker could exploit CVE-2023-23392 by sending a specially crafted packet to a targeted server that utilizes the HTTP Protocol Stack to process packets. For a server to be vulnerable, it must already have HTTP/3 enabled and use buffered I/O. HTTP/3 support for services is a new feature of Windows Server 2022. Another escalation of privilege vulnerability in the same component (CVE-2023-23410) may allow an attacker to elevate privileges to SYSTEM.

CVE-2023-23415 is the only vulnerability among the three with 9.8 CVSS scores that is “more likely” to be exploited, according to Microsoft. An attacker could exploit this vulnerability in the Internet Control Message Protocol (ICMP) to gain the ability to execute remote code with SYSTEM-level privileges.

An attacker could send fragmented ICMP error messages to a remote target and cause a read past the fragment buffer end. This could cause a BSOD if the read crosses a page boundary or give the attacker remote code execution abilities.

The other critical vulnerabilities are:

*   CVE-2023-23404, a remote code execution vulnerability in Windows point-to-point tunneling protocol
*   CVE-2023-23411, a denial-of-service vulnerability in Windows Hyper-V
*   CVE-2023-23416, a remote code execution vulnerability in Windows cryptographic services

A complete list of all the vulnerabilities Microsoft disclosed this month is available on its update page.

In response to these vulnerability disclosures, Talos is releasing a new Snort rule set that detects attempts to exploit some of them. Please note that additional rules may be released at a future date and current rules are subject to change pending additional information. Cisco Secure Firewall customers should use the latest update to their ruleset by updating their SRU. Open-source Snort Subscriber Rule Set customers can stay up to date by downloading the latest rule pack available for purchase on Snort.org.

The rules included in this release that protect against the exploitation of many of these vulnerabilities are 61464 - 61467. The Snort 3 SIDs are 300460 and 300461.

Microsoft Patch Tuesday for March 2023 — Snort rules and prominent vulnerabilities

An agency team will identify vulnerabilities being exploited by ransomware groups and alert organizations ahead of attacks, CISA says.

An anti-ransomware project launched by the Cybersecurity and Infrastructure Security Agency (CISA) will proactively track common vulnerabilities being exploited by ransomware gangs, and alert exposed organizations to the risks to help them mitigate the threat before a cyberattack occurs.

The Ransomware Vulnerability Warning Pilot (RVWP) program started out by alerting 93 organizations open to the recent Microsoft Exchange Service "ProxyNotShell" vulnerability, which was under open attack by ransomware operators in the wild, the CISA announcement explained. The intention is for the RVWP to replicate the model on a larger scale and help critical infrastructure organizations stave off future ransomware attacks.

"Ransomware attacks continue to cause untenable levels of harm to organizations across the country, including target rich, resource poor entities like many school districts and hospitals," Eric Goldstein, executive assistant director for cybersecurity at CISA, said about the program in CISA's announcement. “The RVWP will allow CISA to provide timely and actionable information that will directly reduce the prevalence of damaging ransomware incidents affecting American organizations."

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CISA Trials Ransomware Warning System for Critical Infrastructure Orgs

One researcher thinks trust is broken in AD. Microsoft disagrees that there's a security vulnerability. But enterprise IT environments should be aware of an authentication gap either way.

An access control gap in Microsoft's Active Directory (AD) service may allow users within Windows environments to access domains beyond those for which they are authenticated, all while IT admins are none the wiser.

AD, Microsoft's catchall identity management service for authenticating computers, printers, users, or really anything participating in an IT environment, is built into most Windows domain-type networks. Tens of thousands of organizations use the service, including 90% of Global Fortune 1000 companies, according to Frost & Sullivan.

Network administrators use AD to manage authentication across a domain, ensuring that intended users — _only_ intended users — can access the resources they're allotted — _only_ those they're allotted.

In a report published March 14, however, Charlie Clark, security researcher at Semperis, detailed how a user can escape the guardrails within AD, and access domains for which they were not explicitly granted permission.

"It massively increases the attack surface for an attacker," he explains, "and obviously, the larger the attack surface, the more likely it is that an attacker can find an exploitable bug."

**MSFT AD's "Transitive Trust" Problem**

According to the transitive property of mathematics, if a = b and b = c, then a = c.

In AD, if domain A connects to domain B, and domain B connects to domain C, domains A and C may or may not be able to access one another, depending on whether they share a "transitive trust." As stated in Microsoft's documentation, "transitivity determines whether a trust can be extended outside of the two domains with which it was formed."

Two domains belonging to two different organizations might bear an "external trust" — a form of trust that's set up manually in AD, which is nontransitive. However, herein lies the issue that Clark found: that external trust can be used by one company to access sister domains within the same group (what Microsoft calls a "forest") as the second, for which no official external trust has been established, Clark says.

"If what we thought about non-transitive trusts were true," Clark explains, an authenticated user from one domain would "only be able to target the specific domain they've got a trust with. They wouldn't be able to move around the forest to other domains."

Instead, "any account within the trusted domain will be able to authenticate against any domain within the entire forest in which the trusting domain resides," he wrote in his analysis.

A malicious user who figures out how to burrow around a forest at will can access resources, reach accounts, and find data they otherwise should not.

"It allows an attacker to have a much larger attack surface from any low-privileged account on a trusted domain," Clark reasons, because "if you manage to take over a single domain within a forest, it's very easy to take over the whole forest."

Clark first reported his findings to Microsoft on May 4, 2022. On Sept. 29, Microsoft wrote in an email that "we have determined that this submission does not meet the definition of a security vulnerability for servicing. This report does not appear to identify a weakness in a Microsoft product or service that would enable an attacker to compromise the integrity, availability, or confidentiality of a Microsoft offering." With that, the company closed the case.

“We provide many mechanisms for limiting resource access when using external trusts in a forest trust environment," a Microsoft spokesperson explained. "For example, by applying an authentication policy to resources at any granularity to allow or deny authentication based on any security descriptor. Customers can also set a deny-by-default posture which only allows those users to authenticate to accounts where the user has the allowed-to-authenticate right. We are continuously researching ways to improve security for future releases. More information is available in our authentication policy documentation.”

**Why Trust Matters**

Clark worked as a systems administrator for over 15 years, and a pen tester for six. "Every medium to large business or infrastructure that I've worked with has had external trusts," he claims. By that logic, most of AD's clients are likely at risk right now, he alleges, if additional protections haven't been put in place.

Microsoft's recommendations aside, to protect against this form of access control abuse, Clark recommends that admins remove all external trusts. If this is not possible, then monitoring which users are accessing what is the next best thing.

The most important thing, in the end, is awareness. Otherwise, admins may fall prey to a false sense of security. They "can see that a trusted domain is a higher risk. So they may apply greater security to that domain," Clark explains, but "they might not apply the same level of security to the rest of the domains within the forest," despite the similar risk.

"I think the main thing is to make system admins aware that this is possible," Clark concludes. By knowing this, "they can harden the rest of the domain sufficiently."

Access Control Gap in Microsoft Active Directory Widens Enterprise Attack Surface

Microsoft Outlook Elevation of Privilege Vulnerability

CVE-2023-23397

Microsoft PostScript and PCL6 Class Printer Driver Remote Code Execution Vulnerability

CVE-2023-23413

Microsoft Excel Denial of Service Vulnerability

CVE-2023-23396

CVE-2023-23398

Microsoft Edge (Chromium-based) Webview2 Spoofing Vulnerability

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