{"id":"UBUNTU-CVE-2025-40777","details":"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9.21.9, and 9.20.9-S1 through 9.20.10-S1.","modified":"2026-02-04T04:21:00.727545Z","published":"2025-07-16T00:00:00Z","withdrawn":"2026-01-20T05:33:06Z","related":["USN-7641-1"],"upstream":["CVE-2025-40777"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-40777"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-40777"},{"type":"REPORT","url":"https://kb.isc.org/docs/cve-2025-40777"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-7641-1"}],"affected":[{"package":{"name":"bind9","ecosystem":"Ubuntu:25.04","purl":"pkg:deb/ubuntu/bind9@1:9.20.4-3ubuntu1.2?arch=source&distro=plucky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1:9.20.4-3ubuntu1.2"}]}],"versions":["1:9.20.0-2ubuntu3","1:9.20.0-2ubuntu4","1:9.20.4-3ubuntu1","1:9.20.4-3ubuntu1.1"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"bind9","binary_version":"1:9.20.4-3ubuntu1.2"},{"binary_name":"bind9-dev","binary_version":"1:9.20.4-3ubuntu1.2"},{"binary_name":"bind9-dnsutils","binary_version":"1:9.20.4-3ubuntu1.2"},{"binary_name":"bind9-host","binary_version":"1:9.20.4-3ubuntu1.2"},{"binary_name":"bind9-libs","binary_version":"1:9.20.4-3ubuntu1.2"},{"binary_name":"bind9-utils","binary_version":"1:9.20.4-3ubuntu1.2"},{"binary_version":"1:9.20.4-3ubuntu1.2","binary_name":"bind9utils"},{"binary_name":"dnsutils","binary_version":"1:9.20.4-3ubuntu1.2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-40777.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}