CVE-2026-85091

CVE-2026-85091

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.

Vulnerability class: Buffer Overflow

EPSS: 0.004 (37.0th percentile) — read the EPSS interpretation.