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
0.47% (41st percentile)

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  • Snyk IDSNYK-ALPINE322-ZLIB-20541566
  • 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:3.22 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:3.22 relevant fixed versions and status.

zlib 1.2.11 through 1.3.2 contains a heap buffer overflow: after an underlying write() fails, gz_write() returns without resetting strm.next_in, leaving it pointed at the caller's buffer. A later gz* write call then derives a position from the stale pointer and writes past a heap allocation; any write() failure reaches it, including EPIPE on a blocking descriptor, and in versions before 1.3.1.2 the failed write must be followed by a gzclearerr() call.

CVSS Base Scores

version 3.1