CVE-2025-40777

Public on 2025-07-16

Modified on 2025-07-25

Description

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.

Severity

Important

See what this means

CVSS v3 Base Score

7.5

See breakdown

Affected Packages

Platform	Package	Status
Amazon Linux 1	bind	No Fix Planned
Amazon Linux 2 - Core	bind	Not Affected
Amazon Linux 2023	bind	Pending Fix

CVSS Scores

	Score Type	Score	Vector
Amazon Linux	CVSSv3	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD	CVSSv3	7.5	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

FAQs regarding Amazon Linux ALAS/CVE Severity Red Hat: CVE-2025-40777 Mitre: CVE-2025-40777