Junglewise Threat Intelligence

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

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

Technologies: Gnu Glibc. Vendors: Gnu.

Executive brief

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.

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

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