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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsCVE-2023-6246 is a serious local privilege-escalation flaw in glibc, but an upstream version number alone cannot tell you whether your Linux system is vulnerable. Qualys confirmed vulnerable default installations of Debian 12 and 13, Ubuntu 23.04 and 23.10, and Fedora 37 through 39. Red Hat says its products are not affected. For any installation, check the distribution’s security notice for that exact release and install its supplied update.
What CVE-2023-6246 does
CVE-2023-6246 is a heap-based buffer overflow in glibc’s __vsyslog_internal function, which is used by syslog and vsyslog. Ubuntu Security describes the flaw as an application-crash or local privilege-escalation risk and assigns it CVSS 7.8 (High).
The vulnerable condition involves a program calling the logging function without first calling openlog, or calling it with a null ident, while the program’s basename exceeds 1024 bytes. Qualys demonstrated that an unprivileged local user could exploit the flaw for root access on affected systems. It is a local attack: the attacker needs an execution context on the machine, rather than merely being able to send it a network request.
Which Linux releases were affected?
The following findings are release-specific. Qualys’ 2024 testing confirmed vulnerable default installations for the listed releases; vendor assessments and package updates determine whether a particular installation remains affected. A distribution may backport a fix without changing the upstream version in the way a simple version check expects.
#1 Best Overall
| Distribution and releases | What the sources establish | Fixed package or vendor assessment |
|---|---|---|
| Debian 12 and 13 | Qualys confirmed vulnerable default installations in 2024. Debian’s security tracker and DSA-5611-1 address CVE-2023-6246 alongside CVE-2023-6779 and CVE-2023-6780. | A fixed package version is not stated here; check Debian’s tracker and advisory for the exact release and package status. |
| Ubuntu 23.04 | Qualys confirmed a vulnerable default installation in 2024. | A fixed package version is not stated here; check Ubuntu Security’s notice for this release. |
| Ubuntu 23.10 | Qualys confirmed a vulnerable default installation in 2024. | Ubuntu Security lists 2.38-1ubuntu6.1 as fixed. |
| Ubuntu 24.04 LTS | Ubuntu Security lists the release as fixed. | Fixed at glibc package version 2.39-0ubuntu1, according to Ubuntu Security. |
| Ubuntu 22.04, 20.04, 18.04 and 16.04 | Ubuntu Security marks these releases not affected in its advisory table. | No fix is listed as needed for this CVE in that table. |
| Fedora 37 through 39 | Qualys confirmed vulnerable default installations in 2024. | A fixed package version is not stated here; check Fedora’s release-specific security information. |
| Red Hat products | Red Hat’s official assessment says its products are not affected. | Red Hat attributes this to the issue being introduced in glibc 2.36, a version not used by Red Hat products. |
Sources: Ubuntu Security, Qualys Threat Research Unit, Debian Security Tracker, Debian DSA-5611-1 and Red Hat. The source references available for this article do not include destination URLs, so consult those organizations’ official security pages by CVE number rather than relying on an unverified link.
Why glibc’s version number is not enough
The upstream affected range is glibc 2.36 and newer. That range is a useful clue, not a reliable verdict for a packaged Linux system. Distributions maintain their own package branches and may backport security changes; Red Hat’s unaffected assessment illustrates why the version number by itself can mislead. Conversely, a system with an affected upstream lineage needs the vendor’s package status checked even if its release name is not in a short list of tested installations.
Rank #2
Qualys’ findings identify vulnerable default installations for specific releases, not every installation of every distribution. Package updates, vendor backports, and release differences can change the answer for an individual machine.
How to check and remediate
- Identify the distribution and release. Use your system’s release information or administration tools, then consult that distribution’s official security tracker or advisory for CVE-2023-6246. Do not rely only on the upstream glibc version.
- Check the installed package against the vendor’s fixed status. Ubuntu’s advisory lists fixed package versions for 23.10 and 24.04 LTS; Debian’s tracker and DSA-5611-1 provide release-specific status for Debian. Where a fixed version is not stated above, use the vendor’s current notice for the exact release.
- Install the vendor-provided security update. Use the distribution’s normal package-management process and follow its instructions. Debian’s advisory groups this issue with CVE-2023-6779 and CVE-2023-6780, so include those related glibc issues in the same update review.
- Restart processes that may still use the old library. A running service can retain the old libc mapping after a package is updated. Follow the distribution’s restart guidance and your maintenance policy to restart affected long-running services; do not assume installing the package has replaced libraries already mapped into running processes.
- Include local access in incident triage. Because exploitation requires a local execution context, review who can run programs on the host and investigate unexpected privilege changes while assessing exposure.
Does the update require a reboot?
The available vendor guidance establishes the need to install the fixed package and restart long-running services that still have the old libc mapped; it does not establish a blanket reboot requirement for every distribution or installation. Follow the relevant distribution’s restart guidance and operational policy. If that guidance calls for a reboot, or your environment uses one to ensure all processes reload updated libraries, schedule it accordingly.
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Ubuntu Security’s CVSS 7.8 (High) rating reflects a local attack with low complexity and low privileges, no user interaction, and high potential impact to confidentiality, integrity and availability. Qualys demonstrated escalation from an unprivileged account to root on the affected default installations it tested. That makes patching important wherever the vendor marks the installed release and package as affected, while the local-access requirement helps define how to prioritize exposure and triage.
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