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[USN-7666-1] Unbound vulnerabilities

Posted on 22 July 2025
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-7666-1
July 22, 2025

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

- Ubuntu 25.04
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

The Unbound cache could be poisoned if it received specially crafted
network traffic.

Software Description:
- unbound: validating, recursive, caching DNS resolver

Details:

Xiang Li discovered that Unbound incorrectly handled EDNS Client Subnet
(ECS) in certain configurations. A remote attacker could possibly use this
issue to perform a cache poisoning attack called Rebirthday Attack.

Update instructions:

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

Ubuntu 25.04
libunbound8 1.22.0-1ubuntu1.1
unbound 1.22.0-1ubuntu1.1

Ubuntu 24.04 LTS
libunbound8 1.19.2-1ubuntu3.5
unbound 1.19.2-1ubuntu3.5

Ubuntu 22.04 LTS
libunbound8 1.13.1-1ubuntu5.11
unbound 1.13.1-1ubuntu5.11

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

References:
https://ubuntu.com/security/notices/USN-7666-1
CVE-2025-5994

Package Information:
https://launchpad.net/ubuntu/+source/unbound/1.22.0-1ubuntu1.1
https://launchpad.net/ubuntu/+source/unbound/1.19.2-1ubuntu3.5
https://launchpad.net/ubuntu/+source/unbound/1.13.1-1ubuntu5.11

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