CVE-2026-85091

EUVD-2026-70301
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.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
VulnCheckCNA
7.4 HIGH
NETWORK
HIGH
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 36.99%
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
zlibzlib
1.3.1.2 ≤
𝑥
≤ 1.3.2
CNA
Debian logo
Debian Releases
Debian Product
Codename
zlib
bookworm
vulnerable
forky
vulnerable
sid
vulnerable
trixie
vulnerable
Common Weakness Enumeration
Vulnerability Media Exposure
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-overflow-via-gz-vacate