{"id":"UBUNTU-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":"2026-06-30T18:17:47.153480434Z","published":"2026-05-20T00:00:00Z","related":["USN-8282-1"],"upstream":["CVE-2026-42944"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-42944"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-42944"},{"type":"REPORT","url":"https://nlnetlabs.nl/news/2026/May/20/unbound-1.25.1-released/"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8282-1"}],"affected":[{"package":{"name":"unbound","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/unbound?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.19.2-1ubuntu3.8"}]}],"versions":["1.17.1-2","1.18.0-2ubuntu1","1.18.0-2ubuntu2","1.19.1-1ubuntu1","1.19.2-1ubuntu1","1.19.2-1ubuntu3","1.19.2-1ubuntu3.1","1.19.2-1ubuntu3.2","1.19.2-1ubuntu3.3","1.19.2-1ubuntu3.4","1.19.2-1ubuntu3.5","1.19.2-1ubuntu3.6","1.19.2-1ubuntu3.7"],"ecosystem_specific":{"binaries":[{"binary_name":"libunbound8","binary_version":"1.19.2-1ubuntu3.8"},{"binary_name":"python3-unbound","binary_version":"1.19.2-1ubuntu3.8"},{"binary_name":"unbound","binary_version":"1.19.2-1ubuntu3.8"},{"binary_name":"unbound-anchor","binary_version":"1.19.2-1ubuntu3.8"},{"binary_name":"unbound-host","binary_version":"1.19.2-1ubuntu3.8"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42944.json"}},{"package":{"name":"unbound","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/unbound?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.22.0-2ubuntu2.3"}]}],"versions":["1.22.0-1ubuntu1","1.22.0-2ubuntu1","1.22.0-2ubuntu2","1.22.0-2ubuntu2.1","1.22.0-2ubuntu2.2"],"ecosystem_specific":{"binaries":[{"binary_name":"libunbound8","binary_version":"1.22.0-2ubuntu2.3"},{"binary_name":"python3-unbound","binary_version":"1.22.0-2ubuntu2.3"},{"binary_name":"unbound","binary_version":"1.22.0-2ubuntu2.3"},{"binary_name":"unbound-anchor","binary_version":"1.22.0-2ubuntu2.3"},{"binary_name":"unbound-host","binary_version":"1.22.0-2ubuntu2.3"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42944.json"}},{"package":{"name":"unbound","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/unbound?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.24.2-1ubuntu2.1"}]}],"versions":["1.22.0-2ubuntu2","1.22.0-2ubuntu4","1.24.2-1ubuntu1","1.24.2-1ubuntu2"],"ecosystem_specific":{"binaries":[{"binary_name":"libunbound8","binary_version":"1.24.2-1ubuntu2.1"},{"binary_name":"python3-unbound","binary_version":"1.24.2-1ubuntu2.1"},{"binary_name":"unbound","binary_version":"1.24.2-1ubuntu2.1"},{"binary_name":"unbound-anchor","binary_version":"1.24.2-1ubuntu2.1"},{"binary_name":"unbound-host","binary_version":"1.24.2-1ubuntu2.1"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-42944.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Red"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"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"}]}