{"id":"CVE-2026-41637","details":"In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, client terminated DNS-over-QUIC (DoQ) queries are not accounted properly by Unbound resulting in low-cost inflation of the waiting number of replies for already in-flight resolution queries. This results in degradation of resolution service for new clients for already in-flight queries. A malicious actor can exploit the vulnerability by issuing DoQ queries for query names that need resolution and proceeding on immediately terminating the query by one of STOP_SENDING/RESET_STREAM/CONNECTION_CLOSE QUIC frames. Those terminated DoQ queries are not properly counted for and keep inflating the number of waiting replies for in-flight queries. When the maximum is reached, it results in silent query drops for new clients needing resolution for already in-flight queries. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces. Additionally, a malicious actor needs access to multiple source IPs to bypass the by-default configured 'wait-limit' option.","modified":"2026-08-27T18:26:07.234888669Z","published":"2026-07-22T14:17:18.560Z","related":["SUSE-SU-2026:23050-1","SUSE-SU-2026:23215-1","SUSE-SU-2026:23226-1","openSUSE-SU-2026:11380-1","openSUSE-SU-2026:21550-1"],"references":[{"type":"ADVISORY","url":"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txt"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nlnetlabs/unbound","events":[{"introduced":"0076736fc40298eb6252705e6e158462c6b24d06"},{"fixed":"c33ad1b1a21e48bfe4f140e90252a9be1b0c5745"}],"database_specific":{"cpe":"cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"1.22.0"},{"fixed":"1.25.2"}],"source":"CPE_RANGE"}}],"versions":["release-1.25.1","release-1.25.0","release-1.25.0rc1","release-1.24.0","release-1.24.0rc1","release-1.23.0rc1","release-1.22.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-41637.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:L"}]}