{"id":"CVE-2026-55717","details":"In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a 'response-ip: \u003cnet\u003e redirect' /'response-ip-data: \u003cnet\u003e CNAME \u003ctarget\u003e' rule (or the RPZ 'rpz-cname-override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-timeout' is taken leading to denial of service via the server crash.","modified":"2026-09-10T18:26:55.227967285Z","published":"2026-07-22T14:17:21.537Z","related":["SUSE-SU-2026:23050-1","SUSE-SU-2026:23215-1","SUSE-SU-2026:23226-1","SUSE-SU-2026:23349-1","SUSE-SU-2026:23360-1","SUSE-SU-2026:3884-1","SUSE-SU-2026:3885-1","openSUSE-SU-2026:11380-1","openSUSE-SU-2026:21550-1"],"references":[{"type":"ADVISORY","url":"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-55717.txt"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nlnetlabs/unbound","events":[{"introduced":"6e7717986b25a48952ebb18e131d6eaa005a9757"},{"fixed":"c33ad1b1a21e48bfe4f140e90252a9be1b0c5745"}],"database_specific":{"cpe":"cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"1.10.0"},{"fixed":"1.25.2"}],"source":"CPE_RANGE"}}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55717.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}