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CVE-2023-6779 Fedoraproject CVE debrief

CVE-2023-6779 is an off-by-one heap-based buffer overflow in glibc’s __vsyslog_internal path, which is used by syslog and vsyslog. According to the NVD description, the bug is triggered when these functions process a message larger than INT_MAX bytes, leading to an incorrect buffer-size calculation and potential application crash. NVD rates the issue as HIGH (CVSS 8.2), with no confidentiality impact in the vector and availability as the main concern. The supplied CPE criteria indicate affected glibc versions start at 2.37 and end before 2.39, and Fedora 38/39 are also listed as vulnerable in the source corpus.

Vendor
Fedoraproject
Product
CVE-2023-6779
CVSS
HIGH 8.2
CISA KEV
Not listed in stored evidence
Original CVE published
2024-01-31
Original CVE updated
2026-05-12
Advisory published
2024-01-31
Advisory updated
2026-05-12

Who should care

Linux platform teams, distro maintainers, SREs, and application owners that ship or depend on glibc 2.37 or 2.38. Security teams responsible for Fedora 38/39, and any software that uses syslog/vsyslog in logging paths, should treat this as a priority libc update.

Technical summary

The flaw is described as an off-by-one heap-based buffer overflow in __vsyslog_internal. The vulnerable path is reached through syslog/vsyslog when an extremely large message size causes incorrect allocation logic. The likely observable outcome is a process crash; NVD’s CVSS vector is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H, and NVD maps the weakness to CWE-787, with Red Hat also noting CWE-122. The CPE criteria in the corpus mark gnu:glibc as vulnerable from 2.37 up to, but not including, 2.39, and list Fedora 38 and Fedora 39 as affected.

Defensive priority

High. This is a core libc issue with broad downstream impact and crash potential. Even when the immediate result is denial of service rather than code execution, libc bugs merit rapid remediation because many services share the same dependency.

Recommended defensive actions

  • Upgrade glibc using vendor-packaged fixes as soon as they are available for your distribution.
  • Inventory systems running glibc 2.37 or 2.38, and Fedora 38/39 hosts from the supplied CPE criteria.
  • Review applications that call syslog or vsyslog, especially services that may log attacker-influenced or unusually large messages.
  • Follow vendor advisories and package announcements linked in the corpus, including Red Hat, Fedora, Gentoo, and NetApp references.
  • After patching, validate logging-heavy services with normal regression testing to confirm no crash behavior remains in the affected code path.

Evidence notes

This debrief is based on the supplied NVD record and reference corpus. The core technical description comes from the NVD summary, which states that an off-by-one heap overflow in __vsyslog_internal can occur when syslog/vsyslog are called with messages larger than INT_MAX bytes. The affected-version guidance comes from the supplied CPE criteria for glibc 2.37 through before 2.39 and Fedora 38/39. Supporting references in the corpus include Red Hat’s CVE page, Fedora package announcements, a Red Hat Bugzilla issue, Gentoo’s GLSA, and NetApp’s advisory. Third-party exploit/writeup links are present in the corpus, but this debrief does not claim confirmed exploitation status.

Official resources

Publicly disclosed on 2024-01-31, with the supplied NVD record last modified on 2026-05-12. The corpus includes later vendor and distribution advisories; timing in this debrief follows the CVE publication date, not the generation date.