# CVE-2023-6246: GNU glibc heap buffer overflow in __vsyslog_internal

Source: https://junglewise.ai/threats/cve-2023-6246-gnu-glibc-heap-buffer-overflow-in-vsyslog-internal  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2024-01-31. Updated: 2026-05-12  
License: CC BY 4.0 with a link back

CVE-2023-6246 · Severity: high · CVSS 8.4 · Published 2024-01-31

A vulnerability exists in the GNU C Library (glibc), a fundamental component of Linux systems used by almost all applications for basic tasks like logging. By manipulating how a program starts, a local attacker can cause a memory error that allows them to crash applications or gain full administrative (root) privileges on the system. This poses a significant risk to multi-user environments and servers where unprivileged users might attempt to escalate their access.

Technologies: [Gnu Glibc](https://junglewise.ai/threats/technologies/glibc). Vendors: [Gnu](https://junglewise.ai/threats/vendors/gnu).

## Quick answers

**Is CVE-2023-6246 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2023-6246 being exploited in the wild.

**How severe is CVE-2023-6246?** High severity, with a CVSS score of 8.4, published 31 January 2024.

**Which products and versions are affected?** Gnu Glibc 2.36 and newer.

**Is there a fix for CVE-2023-6246?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2023-6246 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2023-6246?** Check whether you run Gnu Glibc at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-based buffer overflow exists in the __vsyslog_internal function within glibc, which is internally called by syslog() and vsyslog(). The vulnerability is triggered when openlog() is not called (or called with a NULL ident) and the program name (argv[0]) exceeds 1024 bytes. In this state, the function fails to correctly calculate the required buffer size, resulting in a 1-byte malloc() that is subsequently overflowed by the attacker-controlled program name and message content. This can be exploited via SUID-root binaries like 'su' that use PAM (which calls syslog on authentication failure) to achieve local privilege escalation to root. The issue affects glibc versions 2.36 and newer.

## Affected products

- GNU glibc 2.36 and newer

## Timeline

- 2022-08-01: other: Vulnerability introduced in glibc 2.37 and backported to 2.36
- 2024-01-30: disclosed: Advisory published by Qualys
- 2024-01-31: advisory: CVE-2023-6246 assigned and NVD entry created

## References

- [http://packetstormsecurity.com/files/176931/glibc-qsort-Out-Of-Bounds-Read-Write.html](http://packetstormsecurity.com/files/176931/glibc-qsort-Out-Of-Bounds-Read-Write.html)
- [http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html](http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html)
- [http://seclists.org/fulldisclosure/2024/Feb/3](http://seclists.org/fulldisclosure/2024/Feb/3)
- [http://seclists.org/fulldisclosure/2024/Feb/5](http://seclists.org/fulldisclosure/2024/Feb/5)
- [https://access.redhat.com/security/cve/CVE-2023-6246](https://access.redhat.com/security/cve/CVE-2023-6246)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2249053](https://bugzilla.redhat.com/show_bug.cgi?id=2249053)
- [https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/D2FIH77VHY3KCRROCXOT6L27WMZXSJ2G/](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/D2FIH77VHY3KCRROCXOT6L27WMZXSJ2G/)

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