Headline
How to Scan Your Environment for Vulnerable Versions of Curl
This Tech Tip outlines how enterprise defenders can mitigate the risks of the curl and libcurl vulnerabilities in their environments.
Security teams don’t have to swing into crisis mode to address the recently fixed vulnerabilities in the command-line tool curl and the libcurl library, but that doesn’t mean they don’t have to worry about identifying and remediating impacted systems. If the systems are not immediately exploitable, security teams have some time to make those updates.
This Tech Tip aggregates guidance on what security teams need to do to ensure they aren’t at risk.
A foundational networking tool for Unix and Linux systems, cURL is used in command lines and scripts to transfer data. Its prevalence is due to the fact that it is used as both a standalone utility (curl) as well as a library that is included in many different types of applications (libcurl). The libcurl library, which allows developers to access curl APIs from their own code, can be introduced directly into the code, used as a dependency, used as part of an operating system bundle, included as part of a Docker container, or installed on a Kubernetes cluster node.
What Is CVE-2023-38545?
The high severity vulnerability affects curl and libcurl versions 7.69.0 to 8.3.0, and the low severity vulnerability impacts libcurl versions 7.9.1 to 8.3.0. However, the vulnerabilities cannot be exploited under default conditions. An attacker trying to trigger the vulnerability would need to point curl at a malicious server under the attacker’s control, make sure curl is using a SOCKS5 proxy using proxy-resolver mode, configure curl to automatically follow redirects, and set the buffer size to a smaller size.
According to Yair Mizrahi, a senior security researcher at JFrog, the libcurl library is vulnerable only if the following environment variables are set: CURLOPT_PROXYTYPE set to type CURLPROXY_SOCKS5_HOSTNAME; or CURLOPT_PROXY or CURLOPT_PRE_PROXY set to scheme socks5h://. The library is also vulnerable if one of the proxy environment variables is set to use the socks5h:// scheme. The command-line tool is vulnerable only if it is executed with the -socks5-hostname flag, or with –proxy (-x) or –preproxy set to use the scheme socks5h://. It is also vulnerable if curl is executed with the affected environment variables.
“The set of pre-conditions needed in order for a machine to be vulnerable (see previous section) is more restrictive than initially believed. Therefore, we believe the vast majority of curl users won’t be affected by this vulnerability,” Mizrahi wrote in the analysis.
Scan the Environment for Vulnerable Systems
The first thing organizations need to do is to scope their environments to identify all systems using curl and libcurl to assess whether those preconditions exist. Organizations should inventory their systems and evaluate their software delivery processes using software composition analysis tools for code, scanning containers, and application security posture management utilities, notes Alex Ilgayev, head of security research at Cycode. Even though the vulnerability does not affect every implementation of curl, it would be easier to identify the impacted systems if the team starts with a list of potential locations to look.
The following commands identify which versions of curl are installed:
Linux/MacOS:
find / -name curl 2>/dev/null -exec echo “Found: {}” \; -exec {} --version \;
Windows:
Get-ChildItem -Path C:\ -Recurse -ErrorAction SilentlyContinue -Filter curl.exe | ForEach-Object { Write-Host "Found: $($_.FullName)"; & $_.FullName --version }
GitHub has a query to run in Defender for Endpoint to identify all devices in the environment that have curl installed or use curl. Qualys has published its rules for using its platform.
Organizations using Docker containers or other container technologies should also scan the images for vulnerable versions. A sizable number of rebuilds are expected, particularly in docker images and similar entities that incorporate liburl copies. Docker has pulled together a list of instructions on assessing all images.
To find existing repositories:
docker scout repo enable --org <org-name> <org-name>/scout-demo
To analyze local container images:
docker scout policy [IMAGE] --org [ORG]
This issue highlights the importance of keeping meticulous track of all open source software being used in an organization, according to Henrik Plate, a security researcher at Endor Labs.
“Knowing about all the uses of curl and libcurl is the prerequisite for assessing the actual risk and taking remediation actions, be it patching curl, restricting access to affected systems from untrusted networks, or implementing other countermeasures,” Plate said.
If the application comes with a software bill of materials, that would be a good place to start looking for instances of curl, adds John Gallagher, vice president of Viakoo Labs.
Just because the flaws are not exploitable doesn’t mean the updates are not necessary. Patches are available directly for curl and libcurl, and many of the operating systems (Debian, Ubuntu, Red Hat, etc.) have also pushed fixed versions. Keep an eye out for security updates from other applications, as libcurl is a library used by many operating systems and applications.
One workaround until the updates can be deployed is to force curl to use local hostname resolving when connecting to a SOCKS5 proxy, according to JFrog’s Mizrahi. This syntax uses the socks5 scheme and not socks5h: curl -x socks5://someproxy.com. In the library, replace the environment variable CURLPROXY_SOCKS5_HOSTNAME with CURLPROXY_SOCKS5.
According to Benjamin Marr, a security engineer at Intruder, security teams should be monitoring curl flags for excessive large strings, as that would indicate the system had been compromised. The flags are –socks5-hostname, or –proxy or –preproxy set to use the scheme socks5h://.
Related news
Red Hat Security Advisory 2024-2011-03 - Updated Satellite Client packages that fixes Important security bugs and regular bugs are now available for Red Hat Satellite. Issues addressed include a buffer overflow vulnerability.
Red Hat Security Advisory 2024-0797-03 - Updated Satellite 6.14 packages that fixes Important security bugs and several regular bugs are now available for Red Hat Satellite. Issues addressed include HTTP request smuggling, buffer overflow, denial of service, and memory leak vulnerabilities.
Apple Security Advisory 01-22-2024-6 - macOS Ventura 13.6.4 addresses bypass and code execution vulnerabilities.
Apple Security Advisory 01-22-2024-3 - iOS 16.7.5 and iPadOS 16.7.5 addresses code execution vulnerabilities.
Dell vApp Manger, versions prior to 9.2.4.x contain an arbitrary file read vulnerability. A remote attacker could potentially exploit this vulnerability to read arbitrary files from the target system.
Red Hat Security Advisory 2023-7626-03 - Red Hat JBoss Core Services Apache HTTP Server 2.4.57 Service Pack 2 is now available. Issues addressed include buffer overflow, denial of service, information leakage, and integer overflow vulnerabilities.
Red Hat Security Advisory 2023-7625-03 - An update is now available for Red Hat JBoss Core Services. Issues addressed include buffer overflow, denial of service, and information leakage vulnerabilities.
An issue exists in SoftIron HyperCloud where compute nodes may come online immediately without following the correct initialization process. In this instance, workloads may be scheduled on these nodes and deploy to a failed or erroneous state, which impacts the availability of these workloads that may be deployed during this time window. This issue impacts HyperCloud versions from 2.0.0 to before 2.0.3.
Microsoft has released fixes to address 63 security bugs in its software for the month of November 2023, including three vulnerabilities that have come under active exploitation in the wild. Of the 63 flaws, three are rated Critical, 56 are rated Important, and four are rated Moderate in severity. Two of them have been listed as publicly known at the time of the release. The updates are in
Hello everyone! October was an interesting and busy month for me. I started a new job, worked on my open source Vulristics project, and analyzed vulnerabilities using it. Especially Linux vulnerabilities as part of my new Linux Patch Wednesday project. And, of course, analyzed Microsoft Patch Tuesday as well. In addition, at the end of […]
A privilege escalation flaw was found in the node restriction admission plugin of the kubernetes api server of OpenShift. A remote attacker who modifies the node role label could steer workloads from the control plane and etcd nodes onto different worker nodes and gain broader access to the cluster.
This flaw makes curl overflow a heap based buffer in the SOCKS5 proxy handshake. When curl is asked to pass along the host name to the SOCKS5 proxy to allow that to resolve the address instead of it getting done by curl itself, the maximum length that host name can be is 255 bytes. If the host name is detected to be longer, curl switches to local name resolving and instead passes on the resolved address only. Due to this bug, the local variable that means "let the host resolve the name" could get the wrong value during a slow SOCKS5 handshake, and contrary to the intention, copy the too long host name to the target buffer instead of copying just the resolved address there. The target buffer being a heap based buffer, and the host name coming from the URL that curl has been told to operate with.
Ubuntu Security Notice 6429-3 - USN-6429-1 fixed vulnerabilities in curl. This update provides the corresponding updates for Ubuntu 23.10. Jay Satiro discovered that curl incorrectly handled hostnames when using a SOCKS5 proxy. In environments where curl is configured to use a SOCKS5 proxy, a remote attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 22.04 LTS, and Ubuntu 23.04. It was discovered that curl incorrectly handled cookies when an application duplicated certain handles. A local attacker could possibly create a cookie file and inject arbitrary cookies into subsequent connections.
Red Hat Security Advisory 2023-5763-01 - The curl packages provide the libcurl library and the curl utility for downloading files from servers using various protocols, including HTTP, FTP, and LDAP. Issues addressed include a buffer overflow vulnerability.
Red Hat Security Advisory 2023-5700-01 - The curl packages provide the libcurl library and the curl utility for downloading files from servers using various protocols, including HTTP, FTP, and LDAP. Issues addressed include a buffer overflow vulnerability.
By Waqas The company has issued security patches for two vulnerabilities. This is a post from HackRead.com Read the original post: Critical Security Vulnerabilities in Curl Patched, Users Advised to Upgrade
Patches have been released for two security flaws impacting the Curl data transfer library, the most severe of which could potentially result in code execution. The list of vulnerabilities is as follows - CVE-2023-38545 (CVSS score: 7.5) - SOCKS5 heap-based buffer overflow vulnerability CVE-2023-38546 (CVSS score: 5.0) - Cookie injection with none file CVE-2023-38545 is the more severe of the
Touted for days as potentially catastrophic, the curl flaws only impact a narrow set of deployments.
Gentoo Linux Security Advisory 202310-12 - Multiple vulnerabilities have been discovered in curl, the worst of which could result in arbitrary code execution. Versions greater than or equal to 8.3.0-r2 are affected.
Debian Linux Security Advisory 5523-1 - Two security issues were found in Curl, an easy-to-use client-side URL transfer library and command line tool.
Ubuntu Security Notice 6429-1 - Jay Satiro discovered that curl incorrectly handled hostnames when using a SOCKS5 proxy. In environments where curl is configured to use a SOCKS5 proxy, a remote attacker could possibly use this issue to execute arbitrary code. This issue only affected Ubuntu 22.04 LTS, and Ubuntu 23.04. It was discovered that curl incorrectly handled cookies when an application duplicated certain handles. A local attacker could possibly create a cookie file and inject arbitrary cookies into subsequent connections.
The maintainers of the Curl library have released an advisory warning of two forthcoming security vulnerabilities that are expected to be addressed as part of updates released on October 11, 2023. This includes a high severity and a low-severity flaw tracked under the identifiers CVE-2023-38545 and CVE-2023-38546, respectively. Additional details about the issues and the exact version ranges