CVE-2023-6246 is a glibc heap-based buffer overflow that can let a local, unprivileged user escalate to root on affected Linux systems. It is not documented as a practical unauthenticated remote attack: Qualys said the trigger requires an unusually long program name or openlog() identifier. Check your distribution’s tracker and install its package update; upstream version numbers alone are not a reliable way to decide whether a system is affected.
What is CVE-2023-6246?
The flaw is in GNU libc, or glibc, the widely used C library that provides core functions to Linux programs. Specifically, it is a heap-based buffer overflow in __vsyslog_internal(), an internal function called by syslog() and vsyslog(). Canonical and Debian describe the issue as potentially allowing local privilege escalation.
Qualys traced the vulnerable code to a change introduced in glibc 2.37 in August 2022 and backported to glibc 2.36. That history is one reason an upstream version number by itself cannot establish whether a distribution package is vulnerable: vendors maintain their own builds and backport changes.
Can CVE-2023-6246 be exploited remotely?
The supported attack description is local privilege escalation, not remote root access. Qualys said that, to its knowledge, the flaw could not be triggered remotely in a likely scenario because it requires an argv[0] program name or an openlog() ident argument longer than 1024 bytes. The CVSS score does not change that attack-vector qualification.
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How the flaw can lead to root access
When an application has not called openlog(), or calls it with a NULL ident, syslog may use a program name derived from argv[0] in its log header. If that name exceeds the relevant 1024-byte stack buffer, the vulnerable code can allocate a heap buffer that is too small and then overflow it.
Qualys found a path involving su and PAM that allowed it to trigger the condition and demonstrate escalation from an unprivileged account to root on an up-to-date default Fedora 38 amd64 installation. That is a demonstrated configuration, not proof that every Linux installation—or every system in a named distribution family—is exploitable.
Which Linux releases have vendor status information?
Qualys confirmed vulnerability at disclosure in Debian 12 and 13, Ubuntu 23.04 and 23.10, and Fedora 37 through 39. These are historical examples, not a complete or current list of affected releases.
As of October 5, 2026, the vendor trackers list the following statuses and fixed package builds. Use the tracker for your exact distribution and release; package status can differ even when upstream version numbers appear similar.
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| Distribution release | Vendor status or fixed package | Source |
|---|---|---|
| Ubuntu 23.10 | Fixed in 2.38-1ubuntu6.1 |
Canonical CVE tracker |
| Ubuntu 24.04 LTS | Fixed in 2.39-0ubuntu1 |
Canonical CVE tracker |
| Ubuntu 22.04 LTS and 20.04 LTS | Not affected | Canonical CVE tracker |
| Debian Bookworm | Fixed in 2.36-9+deb12u14 |
Debian Security Tracker |
| Debian Trixie | Fixed in 2.41-12+deb13u4 |
Debian Security Tracker |
| Debian Forky/Sid | Fixed in 2.43-6 |
Debian Security Tracker |
| Debian Buster and Bullseye | Not affected; the vulnerable code was absent | Debian Security Tracker |
How to check and update an affected system
- Identify the distribution and release. Use your system’s release information or administration tools so you can select the matching row in the vendor tracker.
- Check the official CVE record. Consult Ubuntu’s tracker, Debian’s tracker, or the security advisory for your Linux distribution. Confirm whether the release is vulnerable, fixed, or not affected.
- Install updates through the distribution’s normal package manager. Apply the vendor’s available security updates rather than trying to replace glibc with a manually selected upstream build.
- Verify the installed package status. Compare the installed package build with the fixed build recorded for your release, or follow your vendor’s stated remediation guidance.
- Follow any restart guidance in the vendor notice. Ubuntu’s USN-6620-1, dated February 1, 2024, listed
2.38-1ubuntu6.1as the fix for Ubuntu 23.10 and instructed users to reboot after a standard system update. That notice is historical; use the current tracker and applicable notice for present-day remediation.
For a fleet, assess each machine using four details: distribution and release, installed package build, vendor status, and whether the host has actually received the update. A distribution name alone is not enough to determine exposure.
How severe is the flaw?
The National Vulnerability Database score reported by The Hacker News is CVSS 7.8; Canonical also lists 7.8 while assigning Ubuntu priority “Medium.” These labels describe severity, not proof of remote exploitability. The attack conditions and the tested local escalation path remain essential context.
Saeed Abbasi, Head of Qualys Threat Research Unit and Director of Product at Qualys, summarized the impact as: “This flaw allows local privilege escalation, enabling an unprivileged user to gain full root access.”
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Related glibc issues are separate CVEs
Qualys also identified CVE-2023-6779, an off-by-one heap buffer overflow, and CVE-2023-6780, an integer overflow, in __vsyslog_internal(). The same advisory discusses a separate qsort() memory-corruption issue. Those findings should not be conflated with CVE-2023-6246 or treated as evidence that this CVE has a different attack path or impact.
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