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CVE-2026-85091

zlib 1.3.1.2 through 1.3.2 Heap Buffer Overflow via gz_vacate

Published: Sep 3, 2026Updated: Sep 9, 2026 Sources: CVE List NVDCWE-787
7.4HIGH
NVD MITRE
EPSS Score
0.4%
Top 62.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
No Fix Available
Self-Check
Not available

Description

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:NI:HA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:HIntegrity
High
A:HAvailability
High
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Weaknesses

CWE-787

Affected Products

zlib
oss-projectaka pigz
zlibLibrary
OSS Libraries / generic-library

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques
Initial Access
Privilege Escalation
View detailed technique mapping

References

https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490
gist.github.com
https://github.com/madler/zlib
github.com
https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393
github.com
and 1 more references View all →
News mentions
1

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