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[USN-8706-1] zlib vulnerability

Posted on 01 September 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8706-1
August 31, 2026

zlib vulnerability
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS

Summary:

zlib could be made to consume excessive CPU resources if it received
specially crafted input.

Software Description:
- zlib: Lossless data-compression library

Details:

It was discovered that zlib incorrectly handled negative length parameters
in CRC32 combine functions. An attacker could use this issue to cause a denial
of service via excessive CPU consumption.

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
lib32z1 1:1.3.dfsg+really1.3.1-1ubuntu3.1
lib32z1-dev 1:1.3.dfsg+really1.3.1-1ubuntu3.1
lib64z1 1:1.3.dfsg+really1.3.1-1ubuntu3.1
lib64z1-dev 1:1.3.dfsg+really1.3.1-1ubuntu3.1
libminizip-dev 1:1.3.dfsg+really1.3.1-1ubuntu3.1
libminizip1t64 1:1.3.dfsg+really1.3.1-1ubuntu3.1
libx32z1 1:1.3.dfsg+really1.3.1-1ubuntu3.1
libx32z1-dev 1:1.3.dfsg+really1.3.1-1ubuntu3.1
minizip 1:1.3.dfsg+really1.3.1-1ubuntu3.1
zlib1g 1:1.3.dfsg+really1.3.1-1ubuntu3.1
zlib1g-dev 1:1.3.dfsg+really1.3.1-1ubuntu3.1

Ubuntu 24.04 LTS
lib32z1 1:1.3.dfsg-3.1ubuntu2.2
lib32z1-dev 1:1.3.dfsg-3.1ubuntu2.2
lib64z1 1:1.3.dfsg-3.1ubuntu2.2
lib64z1-dev 1:1.3.dfsg-3.1ubuntu2.2
libminizip-dev 1:1.3.dfsg-3.1ubuntu2.2
libminizip1t64 1:1.3.dfsg-3.1ubuntu2.2
libx32z1 1:1.3.dfsg-3.1ubuntu2.2
libx32z1-dev 1:1.3.dfsg-3.1ubuntu2.2
minizip 1:1.3.dfsg-3.1ubuntu2.2
zlib1g 1:1.3.dfsg-3.1ubuntu2.2
zlib1g-dev 1:1.3.dfsg-3.1ubuntu2.2

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8706-1
CVE-2026-27171

Package Information:
https://launchpad.net/ubuntu/+source/zlib/1:1.3.dfsg+really1.3.1-1ubuntu3.1
https://launchpad.net/ubuntu/+source/zlib/1:1.3.dfsg-3.1ubuntu2.2

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