Out-of-bounds Write Affecting zlib package, versions <1.3.2-r1


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.36% (28th percentile)

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  • Snyk IDSNYK-ALPINE323-ZLIB-20541565
  • published7 Oct 2026
  • disclosed3 Sept 2026

Introduced: 3 Sep 2026

CVE-2026-85091  (opens in a new tab)
CWE-787  (opens in a new tab)

How to fix?

Upgrade Alpine:3.23 zlib to version 1.3.2-r1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream zlib package and not the zlib package as distributed by Alpine. See How to fix? for Alpine:3.23 relevant fixed versions and status.

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 Base Scores

version 3.1