Vulnerability Description
zlib versions 1.3.1.2 through 1.3.2 contain a heap buffer overflow vulnerability in the gz_vacate() function when processing non-blocking gzwrite() operations with stale external buffer pointers. Attackers can trigger the overflow by calling gzprintf() or gzvprintf() after a write stall, causing an unchecked memmove() to write beyond the internal input buffer boundary.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490
- https://github.com/madler/zlib
- https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393
- https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-over
FAQ
What is CVE-2026-85091?
CVE-2026-85091 is a vulnerability with a CVSS score of 7.4 (HIGH). zlib versions 1.3.1.2 through 1.3.2 contain a heap buffer overflow vulnerability in the gz_vacate() function when processing non-blocking gzwrite() operations with stale external buffer pointers. Atta...
How severe is CVE-2026-85091?
CVE-2026-85091 has been rated HIGH with a CVSS base score of 7.4/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-85091?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.