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[USN-8521-1] Libidn vulnerability

Posted on 09 July 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8521-1
July 09, 2026

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

- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

Libidn could be made to crash or expose sensitive information if it
received specially crafted input.

Software Description:
- libidn: implementation of IETF IDN specifications

Details:

It was discovered that Libidn incorrectly handled certain internationalized
domain name strings. An attacker could possibly use this issue to obtain
sensitive information or cause a denial of service.

Update instructions:

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

Ubuntu 26.04 LTS
libidn12 1.43-2ubuntu0.26.04.1

Ubuntu 24.04 LTS
libidn12 1.42-1ubuntu0.1

Ubuntu 22.04 LTS
libidn12 1.38-4ubuntu1.1

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

References:
https://ubuntu.com/security/notices/USN-8521-1
CVE-2026-57053

Package Information:
https://launchpad.net/ubuntu/+source/libidn/1.43-2ubuntu0.26.04.1
https://launchpad.net/ubuntu/+source/libidn/1.42-1ubuntu0.1
https://launchpad.net/ubuntu/+source/libidn/1.38-4ubuntu1.1

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