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[USN-7959-1] klibc vulnerabilities

Posted on 14 January 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-7959-1
January 14, 2026

klibc vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 25.10
- Ubuntu 25.04
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS

Summary:

klibc could be made to crash if it received specially crafted input.

Software Description:
- klibc: Minimalistic libc subset for use with initramfs

Details:

It was discovered that zlib, vendored in klibc, did not properly handle
integer arithmetic. An attacker could possibly use this issue to execute
arbitrary code or cause a denial of service.

Update instructions:

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

Ubuntu 25.10
klibc-utils 2.0.14-1ubuntu1.1
libklibc 2.0.14-1ubuntu1.1

Ubuntu 25.04
klibc-utils 2.0.13-4ubuntu1.1
libklibc 2.0.13-4ubuntu1.1

Ubuntu 24.04 LTS
klibc-utils 2.0.13-4ubuntu0.2
libklibc 2.0.13-4ubuntu0.2

Ubuntu 22.04 LTS
klibc-utils 2.0.10-4ubuntu0.2
libklibc 2.0.10-4ubuntu0.2

Ubuntu 20.04 LTS
klibc-utils 2.0.7-1ubuntu5.2+esm1
Available with Ubuntu Pro
libklibc 2.0.7-1ubuntu5.2+esm1
Available with Ubuntu Pro

Ubuntu 18.04 LTS
klibc-utils 2.0.4-9ubuntu2.2+esm2
Available with Ubuntu Pro
libklibc 2.0.4-9ubuntu2.2+esm2
Available with Ubuntu Pro

Ubuntu 16.04 LTS
klibc-utils 2.0.4-8ubuntu1.16.04.4+esm3
Available with Ubuntu Pro
libklibc 2.0.4-8ubuntu1.16.04.4+esm3
Available with Ubuntu Pro

Ubuntu 14.04 LTS
klibc-utils 2.0.3-0ubuntu1.14.04.3+esm4
Available with Ubuntu Pro
libklibc 2.0.3-0ubuntu1.14.04.3+esm4
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-7959-1
CVE-2016-9843

Package Information:
https://launchpad.net/ubuntu/+source/klibc/2.0.14-1ubuntu1.1
https://launchpad.net/ubuntu/+source/klibc/2.0.13-4ubuntu1.1
https://launchpad.net/ubuntu/+source/klibc/2.0.13-4ubuntu0.2
https://launchpad.net/ubuntu/+source/klibc/2.0.10-4ubuntu0.2

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