CVE-2025-5994 Affecting unbound-devel package, versions <0:1.16.2-5.9.el8


Severity

Recommended
high

Based on Rocky Linux security rating.

Threat Intelligence

EPSS
0.22% (12th percentile)

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  • Snyk IDSNYK-ROCKY8-UNBOUNDDEVEL-17094583
  • published30 May 2026
  • disclosed16 Jul 2025

Introduced: 16 Jul 2025

CVE-2025-5994  (opens in a new tab)

How to fix?

Upgrade Rocky-Linux:8 unbound-devel to version 0:1.16.2-5.9.el8 or higher.
This issue was patched in RLSA-2025:11884.

NVD Description

Note: Versions mentioned in the description apply only to the upstream unbound-devel package and not the unbound-devel package as distributed by Rocky-Linux. See How to fix? for Rocky-Linux:8 relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1