If a `named` caching resolver is configured with `serve-stale-enable` `yes`, and with `stale-answer-client-timeout` set to `0` (the only allowable value other than `disabled`), and if the resolver, in the process of resolving a query, encounters a CNAME chain involving a specific combination of cached or authoritative records, the daemon will abort with an assertion failure.
This issue affects BIND 9 versions 9.20.0 through 9.20.10, 9.21.0 through 9.21.9, and 9.20.9-S1 through 9.20.10-S1.

Related CVEs

CVE-2025-40777

Key Information

GHSA ID

GHSA-4x4c-8qp9-8ggh

Published

July 16, 2025 6:32 PM

Last Modified

July 16, 2025 6:32 PM

CVSS Score

7.5 /10

Primary Ecosystem

Unknown

Primary Package

Unknown

GitHub Reviewed

✗ No

Dataset

Last updated: September 19, 2025 6:29 AM

Data from GitHub Advisory Database. This information is provided for research and educational purposes.