Out-of-bounds Write Affecting zlib package, versions <1.3.3-r0


Severity

Recommended
0.0
high
0
10

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Threat Intelligence

EPSS
0.44% (37th percentile)

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  • Snyk IDSNYK-CHAINGUARDLATEST-ZLIB-19706428
  • published12 Sept 2026
  • disclosed3 Sept 2026

Introduced: 3 Sep 2026

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

How to fix?

Upgrade Chainguard zlib to version 1.3.3-r0 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 Chainguard. See How to fix? for Chainguard 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