CVE-2025-5994 Information

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.

Reference

https://nlnetlabs.nl/downloads/unbound/CVE-2025-5994.txt

Related CNNVD

CNNVD-202507-2097 (Published: 2025-07-16)