{"id":"CVE-2025-40777","state":"PUBLISHED","title":"A possible assertion failure when 'stale-answer-client-timeout' is set to '0'","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.\nThis 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.","publishedAt":"2025-07-16T17:38:06.370Z","updatedAt":"2025-11-04T21:10:12.751Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"isc"},"assigner":"isc","products":["ISC BIND 9"],"affected":[{"vendor":"ISC","product":"BIND 9","defaultStatus":"unaffected","versions":[{"version":"9.20.0","status":"affected","lessThanOrEqual":"9.20.10","versionType":"custom"},{"version":"9.21.0","status":"affected","lessThanOrEqual":"9.21.9","versionType":"custom"},{"version":"9.20.9-S1","status":"affected","lessThanOrEqual":"9.20.10-S1","versionType":"custom"},{"version":"9.18.0","status":"unaffected","lessThanOrEqual":"9.18.37","versionType":"custom"},{"version":"9.18.11-S1","status":"unaffected","lessThanOrEqual":"9.18.37-S1","versionType":"custom"}]}],"references":["https://kb.isc.org/docs/cve-2025-40777","http://www.openwall.com/lists/oss-security/2025/07/16/6"],"weaknesses":["CWE-617"],"ingestedAt":"2026-10-29T20:09:09.358Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2025/40xxx/CVE-2025-40777.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2025-40777","state":"PUBLISHED","datePublished":"2025-07-16T17:38:06.370Z","dateUpdated":"2025-11-04T21:10:12.751Z","assignerShortName":"isc","assignerOrgId":"404fd4d2-a609-4245-b543-2c944a302a22","dateReserved":"2025-04-16T08:44:49.856Z"},"containers":{"cna":{"title":"A possible assertion failure when 'stale-answer-client-timeout' is set to '0'","descriptions":[{"lang":"en","value":"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.\nThis 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."}],"affected":[{"vendor":"ISC","product":"BIND 9","defaultStatus":"unaffected","versions":[{"version":"9.20.0","status":"affected","lessThanOrEqual":"9.20.10","versionType":"custom"},{"version":"9.21.0","status":"affected","lessThanOrEqual":"9.21.9","versionType":"custom"},{"version":"9.20.9-S1","status":"affected","lessThanOrEqual":"9.20.10-S1","versionType":"custom"},{"version":"9.18.0","status":"unaffected","lessThanOrEqual":"9.18.37","versionType":"custom"},{"version":"9.18.11-S1","status":"unaffected","lessThanOrEqual":"9.18.37-S1","versionType":"custom"}]}],"references":[{"url":"https://kb.isc.org/docs/cve-2025-40777","name":"CVE-2025-40777","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"version":"3.1","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-617","lang":"en","type":"CWE","description":"CWE-617 Reachable Assertion"}]}],"providerMetadata":{"shortName":"isc","orgId":"404fd4d2-a609-4245-b543-2c944a302a22","dateUpdated":"2025-07-16T17:38:06.370Z"},"datePublic":"2025-07-16T00:00:00.000Z","impacts":[{"descriptions":[{"lang":"en","value":"If an attacker is able to make queries that yield the necessary combination of circumstances, they can force `named` to exit."}]}],"workarounds":[{"lang":"en","value":"Setting either of `stale-answer-client-timeout off;` or `stale-answer-enable no;` in the configuration file will prevent the assertion."}],"exploits":[{"lang":"en","value":"This flaw was discovered in internal testing. We are not aware of any active exploits."}],"solutions":[{"lang":"en","value":"Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.11, 9.21.10, or 9.20.11-S1."}],"source":{"discovery":"INTERNAL"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2025-07-18T14:25:41.033326Z","id":"CVE-2025-40777","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2025-07-18T14:25:48.883Z"}},{"title":"CVE Program Container","references":[{"url":"http://www.openwall.com/lists/oss-security/2025/07/16/6"}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2025-11-04T21:10:12.751Z"}}]}}}