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Ubuntu 25.10: klibc Critical Integer Arithmetic DoS USN-7959-1

ubuntu
Calendar Grey January 14, 2026
Dist Ubuntu Esm H88
Update klibc for Ubuntu to fix critical integer arithmetic issues leading to crashes and potential DoS.
klibc could be made to crash if it received specially crafted input.

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.

Topics%20covered

Topics Covered

security advisory denial of service critical software update Ubuntu klibc

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

Severity
critical
Lowest
Low
Medium
High
Critical

Ubuntu Security Notice USN-7959-1

Topics%20covered

Topics Covered

security advisory denial of service critical software update Ubuntu klibc

Package Information

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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