CVE-2026-85091CWE-787

CVE-2026-85091

High · published September 3, 2026

CVSS v3.1
7.4
EPSS
0%
Percentile
28.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.4 · HIGH
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H
CVSS v4.0
8.3 · CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N
EPSS
0.00356 · 28.1th percentile
Weakness
CWE-787 · Out-of-bounds Write
Published
2026-09-03T17:06Z
References (4)
https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490 · [email protected]https://github.com/madler/zlib · [email protected]https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393 · [email protected]https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate · [email protected]
EPSS history
Timeline
  • 04 SEP 03:44Z
    EPSS moved — → 0%
    epss
  • 03 SEP 01:04Z
    zlib 1.3.1.2 through 1.3.2 Heap Buffer Overflow via gz_vacate
    cvelistv5