{"id":"UBUNTU-CVE-2026-33278","details":"NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep-copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.","modified":"2026-06-30T18:17:54.637620615Z","published":"2026-05-20T00:00:00Z","related":["USN-8282-1"],"upstream":["CVE-2026-33278"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-33278"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-33278"},{"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_version":"1.19.2-1ubuntu3.8","binary_name":"libunbound8"},{"binary_name":"python3-unbound","binary_version":"1.19.2-1ubuntu3.8"},{"binary_version":"1.19.2-1ubuntu3.8","binary_name":"unbound"},{"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","priority_reason":"Possible remote code execution"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33278.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_version":"1.22.0-2ubuntu2.3","binary_name":"libunbound8"},{"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","priority_reason":"Possible remote code execution"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33278.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_version":"1.24.2-1ubuntu2.1","binary_name":"unbound"},{"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","priority_reason":"Possible remote code execution"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33278.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:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:U/U:Red"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"high"}]}