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Klibc: 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()… (CVE-2026-85091)

0
Medium
VulnerabilityCVE-2026-85091gcveosvubuntu-cve-2026-85091cve-2026-85091ubuntu-pro-14-04-ltsubuntu-pro-16-04-ltsubuntu-16-04-ltsubuntu-pro-18-04-ltsubuntu-18-04-ltsubuntu-pro-20-04-ltsubuntu-20-04-ltsubuntu-22-04-ltsubuntu-24-04-ltsubuntu-26-04-lts
Published: 09/04/2026 (09/04/2026, 00:00:00 UTC)
Source: GCVE Database
Product: klibc

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.

CVSS v3.1

Score 7.4high

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
High
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:H

Affected software

Ubuntu:Pro:14.04:LTSmore threats →ghsa
klibc
pkg:deb/ubuntu/klibc?arch=source&distro=esm-infra-legacy/trusty
Affected versions
=2.0.1-3.1ubuntu2=2.0.2-1ubuntu1=2.0.2-1ubuntu2=2.0.3-0ubuntu1=2.0.3-0ubuntu1.14.04.1=2.0.3-0ubuntu1.14.04.2=2.0.3-0ubuntu1.14.04.3=2.0.3-0ubuntu1.14.04.3+esm2=2.0.3-0ubuntu1.14.04.3+esm3=2.0.3-0ubuntu1.14.04.3+esm4
Ubuntu:Pro:14.04:LTSmore threats →ghsa
zlib
pkg:deb/ubuntu/zlib?arch=source&distro=esm-infra-legacy/trusty
Affected versions
=1:1.2.8.dfsg-1ubuntu1=1:1.2.8.dfsg-1ubuntu1.1=1:1.2.8.dfsg-1ubuntu1.1+esm1=1:1.2.8.dfsg-1ubuntu1.1+esm2=1:1.2.8.dfsg-1ubuntu1.1+esm3
Ubuntu:Pro:16.04:LTSmore threats →ghsa
klibc
pkg:deb/ubuntu/klibc?arch=source&distro=esm-infra/xenial
Affected versions
=2.0.3-0ubuntu1=2.0.4-4=2.0.4-6=2.0.4-7=2.0.4-8=2.0.4-8ubuntu1=2.0.4-8ubuntu1.16.04.1=2.0.4-8ubuntu1.16.04.2=2.0.4-8ubuntu1.16.04.3=2.0.4-8ubuntu1.16.04.4=2.0.4-8ubuntu1.16.04.4+esm1=2.0.4-8ubuntu1.16.04.4+esm2=2.0.4-8ubuntu1.16.04.4+esm3
Ubuntu:Pro:16.04:LTSmore threats →ghsa
rsync
pkg:deb/ubuntu/rsync?arch=source&distro=esm-infra-legacy/xenial
Affected versions
=3.1.1-3=3.1.1-3ubuntu1=3.1.1-3ubuntu1.1=3.1.1-3ubuntu1.2=3.1.1-3ubuntu1.3=3.1.1-3ubuntu1.3+esm1=3.1.1-3ubuntu1.3+esm2=3.1.1-3ubuntu1.3+esm3=3.1.1-3ubuntu1.3+esm4=3.1.1-3ubuntu1.3+esm5=3.1.1-3ubuntu1.3+esm6
Ubuntu:Pro:16.04:LTSmore threats →ghsa
zlib
pkg:deb/ubuntu/zlib?arch=source&distro=esm-infra/xenial
Affected versions
=1:1.2.8.dfsg-2ubuntu4=1:1.2.8.dfsg-2ubuntu4.1=1:1.2.8.dfsg-2ubuntu4.3=1:1.2.8.dfsg-2ubuntu4.3+esm1=1:1.2.8.dfsg-2ubuntu4.3+esm2
Ubuntu:16.04:LTSmore threats →ghsa
zsync
pkg:deb/ubuntu/zsync?arch=source&distro=xenial
Affected versions
=0.6.2-1ubuntu1
Ubuntu:Pro:18.04:LTSmore threats →ghsa
klibc
pkg:deb/ubuntu/klibc?arch=source&distro=esm-infra/bionic
Affected versions
=2.0.4-9ubuntu1=2.0.4-9ubuntu2=2.0.4-9ubuntu2.1=2.0.4-9ubuntu2.2=2.0.4-9ubuntu2.2+esm1=2.0.4-9ubuntu2.2+esm2
Ubuntu:Pro:18.04:LTSmore threats →ghsa
rsync
pkg:deb/ubuntu/rsync?arch=source&distro=esm-infra/bionic
Affected versions
=3.1.2-2=3.1.2-2.1=3.1.2-2.1ubuntu1=3.1.2-2.1ubuntu1.1=3.1.2-2.1ubuntu1.2=3.1.2-2.1ubuntu1.3=3.1.2-2.1ubuntu1.4=3.1.2-2.1ubuntu1.5=3.1.2-2.1ubuntu1.6=3.1.2-2.1ubuntu1.6+esm1=3.1.2-2.1ubuntu1.6+esm2=3.1.2-2.1ubuntu1.6+esm3=3.1.2-2.1ubuntu1.6+esm4
Ubuntu:18.04:LTSmore threats →ghsa
zlib
pkg:deb/ubuntu/zlib?arch=source&distro=bionic
Affected versions
=1:1.2.11.dfsg-0ubuntu2=1:1.2.11.dfsg-0ubuntu2.1=1:1.2.11.dfsg-0ubuntu2.2
Ubuntu:18.04:LTSmore threats →ghsa
zsync
pkg:deb/ubuntu/zsync?arch=source&distro=bionic
Affected versions
=0.6.2-2ubuntu1=0.6.2-3ubuntu1
Ubuntu:Pro:20.04:LTSmore threats →ghsa
klibc
pkg:deb/ubuntu/klibc?arch=source&distro=esm-infra/focal
Affected versions
=2.0.6-1ubuntu1=2.0.6-1ubuntu2=2.0.7-1ubuntu1=2.0.7-1ubuntu3=2.0.7-1ubuntu4=2.0.7-1ubuntu5=2.0.7-1ubuntu5.1=2.0.7-1ubuntu5.2=2.0.7-1ubuntu5.2+esm1
Ubuntu:Pro:20.04:LTSmore threats →ghsa
rsync
pkg:deb/ubuntu/rsync?arch=source&distro=esm-infra/focal
Affected versions
=3.1.3-6=3.1.3-8=3.1.3-8ubuntu0.1=3.1.3-8ubuntu0.2=3.1.3-8ubuntu0.3=3.1.3-8ubuntu0.4=3.1.3-8ubuntu0.5=3.1.3-8ubuntu0.7=3.1.3-8ubuntu0.8=3.1.3-8ubuntu0.9=3.1.3-8ubuntu0.9+esm1=3.1.3-8ubuntu0.9+esm2
Ubuntu:20.04:LTSmore threats →ghsa
zlib
pkg:deb/ubuntu/zlib?arch=source&distro=focal
Affected versions
=1:1.2.11.dfsg-1ubuntu3=1:1.2.11.dfsg-2ubuntu1=1:1.2.11.dfsg-2ubuntu1.1=1:1.2.11.dfsg-2ubuntu1.2=1:1.2.11.dfsg-2ubuntu1.3=1:1.2.11.dfsg-2ubuntu1.4=1:1.2.11.dfsg-2ubuntu1.5
Ubuntu:20.04:LTSmore threats →ghsa
zsync
pkg:deb/ubuntu/zsync?arch=source&distro=focal
Affected versions
=0.6.2-3ubuntu1
Ubuntu:22.04:LTSmore threats →ghsa
klibc
pkg:deb/ubuntu/klibc?arch=source&distro=jammy
Affected versions
=2.0.8-6.1ubuntu2=2.0.10-3=2.0.10-4=2.0.10-4ubuntu0.1=2.0.10-4ubuntu0.2
Ubuntu:22.04:LTSmore threats →ghsa
zlib
pkg:deb/ubuntu/zlib?arch=source&distro=jammy
Affected versions
=1:1.2.11.dfsg-2ubuntu7=1:1.2.11.dfsg-2ubuntu9=1:1.2.11.dfsg-2ubuntu9.1=1:1.2.11.dfsg-2ubuntu9.2
Ubuntu:22.04:LTSmore threats →ghsa
zsync
pkg:deb/ubuntu/zsync?arch=source&distro=jammy
Affected versions
=0.6.2-3ubuntu1
Ubuntu:24.04:LTSmore threats →ghsa
klibc
pkg:deb/ubuntu/klibc?arch=source&distro=noble
Affected versions
=2.0.13-1=2.0.13-2=2.0.13-2ubuntu1=2.0.13-4=2.0.13-4ubuntu0.1=2.0.13-4ubuntu0.2
Ubuntu:24.04:LTSmore threats →ghsa
zlib
pkg:deb/ubuntu/zlib?arch=source&distro=noble
Affected versions
=1:1.2.13.dfsg-1ubuntu5=1:1.3.dfsg-3ubuntu1=1:1.3.dfsg-3.1ubuntu1=1:1.3.dfsg-3.1ubuntu2=1:1.3.dfsg-3.1ubuntu2.1=1:1.3.dfsg-3.1ubuntu2.2
Ubuntu:24.04:LTSmore threats →ghsa
zsync
pkg:deb/ubuntu/zsync?arch=source&distro=noble
Affected versions
=0.6.2-5=0.6.2-5build1
Ubuntu:26.04:LTSmore threats →ghsa
klibc
pkg:deb/ubuntu/klibc?arch=source&distro=resolute
Affected versions
=2.0.14-1ubuntu1=2.0.14-1ubuntu2
Ubuntu:26.04:LTSmore threats →ghsa
zlib
pkg:deb/ubuntu/zlib?arch=source&distro=resolute
Affected versions
=1:1.3.dfsg+really1.3.1-1ubuntu2=1:1.3.dfsg+really1.3.1-1ubuntu3=1:1.3.dfsg+really1.3.1-1ubuntu3.1
Ubuntu:26.04:LTSmore threats →ghsa
zsync
pkg:deb/ubuntu/zsync?arch=source&distro=resolute
Affected versions
=0.6.2-8=0.6.2-9

Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.

Technical Details

Gcve Source
db.gcve.eu
Osv Id
UBUNTU-CVE-2026-85091
Osv Schema Version
1.7.0
Ecosystems
["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:26.04:LTS"]
Cvss Version
3.1

Threat ID: 6aa47ebf55bf5e2cf58579e4

Added to database: 09/11/2026, 22:20:47 UTC

Last updated: 09/12/2026, 01:42:11 UTC

Views: 3

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