CVE-2025-5994

Publication date 17 July 2025

Last updated 22 July 2025

Ubuntu priority

Medium

Why this priority?

Description

A multi-vendor cache poisoning vulnerability named 'Rebirthday Attack' has been discovered in caching resolvers that support EDNS Client Subnet (ECS). Unbound is also vulnerable when compiled with ECS support, i.e., '--enable-subnet', AND configured to send ECS information along with queries to upstream name servers, i.e., at least one of the 'send-client-subnet', 'client-subnet-zone' or 'client-subnet-always-forward' options is used. Resolvers supporting ECS need to segregate outgoing queries to accommodate for different outgoing ECS information. This re-opens up resolvers to a birthday paradox attack (Rebirthday Attack) that tries to match the DNS transaction ID in order to cache non-ECS poisonous replies.

Status

Package Ubuntu Release Status
unbound 25.10 questing
Fixed 1.22.0-2ubuntu1
25.04 plucky
Fixed 1.22.0-1ubuntu1.1
24.04 LTS noble
Fixed 1.19.2-1ubuntu3.5
22.04 LTS jammy
Fixed 1.13.1-1ubuntu5.11
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty
Needs evaluation

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
unbound

References

Related Ubuntu Security Notices (USN)

Other references