{"id":"CVE-2026-42944","details":"NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.","modified":"2026-07-08T08:12:35.231146969Z","published":"2026-05-20T10:16:27.760Z","related":["ALSA-2026:23231","ALSA-2026:24365","ALSA-2026:24369","SUSE-SU-2026:21874-1","SUSE-SU-2026:21913-1","SUSE-SU-2026:22160-1","SUSE-SU-2026:22213-1","SUSE-SU-2026:2281-1","SUSE-SU-2026:2369-1","openSUSE-SU-2026:10903-1","openSUSE-SU-2026:21083-1"],"database_specific":{},"references":[{"type":"WEB","url":"https://access.redhat.com/security/cve/CVE-2026-42944"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42944.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:19752"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:23231"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:24365"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:24369"},{"type":"ADVISORY","url":"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42944.txt"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2479774"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/nlnetlabs/unbound","events":[{"introduced":"919c8c9527281a7289415c00f8f2aed12b17a9aa"},{"fixed":"75b6dba593d4fff000434cd64807c6ebd50bd244"}],"database_specific":{"cpe":"cpe:2.3:a:nlnetlabs:unbound:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"1.14.0"},{"fixed":"1.25.1"}],"source":"CPE_RANGE"}}],"versions":["release-1.25.0","release-1.25.0rc1","release-1.24.0","release-1.24.0rc1","release-1.23.0rc1","release-1.22.0","release-1.22.0rc1","release-1.21.0","release-1.21.0rc1","release-1.20.0rc1","release-1.20.0","release-1.19.3rc1","release-1.19.0rc1","release-1.19.0","release-1.18.0","release-1.18.0rc1","release-1.16.2","release-1.16.1rc1","release-1.16.1","release-1.16.0rc1","release-1.16.0","release-1.15.0rc1","release-1.15.0","release-1.14.0rc1","release-1.14.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42944.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}