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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.

PUBLISHED Reserved 2025-04-16 | Published 2025-07-16 | Updated 2025-11-04 | Assigner isc




HIGH: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-617 Reachable Assertion

Product status

Default status
unaffected

9.20.0 (custom)
affected

9.21.0 (custom)
affected

9.20.9-S1 (custom)
affected

9.18.0 (custom)
unaffected

9.18.11-S1 (custom)
unaffected

References

www.openwall.com/lists/oss-security/2025/07/16/6

kb.isc.org/docs/cve-2025-40777 (CVE-2025-40777) vendor-advisory

cve.org (CVE-2025-40777)

nvd.nist.gov (CVE-2025-40777)

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