{"id":"UBUNTU-CVE-2025-31498","details":"c-ares is an asynchronous resolver library. From 1.32.3 through 1.34.4, there is a use-after-free in read_answers() when process_answer() may re-enqueue a query either due to a DNS Cookie Failure or when the upstream server does not properly support EDNS, or possibly on TCP queries if the remote closed the connection immediately after a response. If there was an issue trying to put that new transaction on the wire, it would close the connection handle, but read_answers() was still expecting the connection handle to be available to possibly dequeue other responses. In theory a remote attacker might be able to trigger this by flooding the target with ICMP UNREACHABLE packets if they also control the upstream nameserver and can return a result with one of those conditions, this has been untested. Otherwise only a local attacker might be able to change system behavior to make send()/write() return a failure condition. This vulnerability is fixed in 1.34.5.","modified":"2026-01-30T01:46:12.437710Z","published":"2025-04-08T14:15:00Z","withdrawn":"2026-01-20T05:27:25Z","related":["USN-7477-1"],"upstream":["CVE-2025-31498"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2025-31498"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2025-31498"},{"type":"REPORT","url":"https://github.com/c-ares/c-ares/security/advisories/GHSA-6hxc-62jh-p29v"},{"type":"REPORT","url":"http://www.openwall.com/lists/oss-security/2025/04/08/3"},{"type":"REPORT","url":"https://github.com/c-ares/c-ares/commit/29d38719112639d8c0ba910254a3dd4f482ea2d1"},{"type":"REPORT","url":"https://github.com/c-ares/c-ares/pull/821"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-7477-1"}],"affected":[{"package":{"name":"c-ares","ecosystem":"Ubuntu:25.04","purl":"pkg:deb/ubuntu/c-ares@1.34.4-2.1ubuntu0.1?arch=source&distro=plucky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.34.4-2.1ubuntu0.1"}]}],"versions":["1.33.0-1","1.34.2-1","1.34.3-1","1.34.4-1","1.34.4-2.1"],"ecosystem_specific":{"availability":"No subscription required","binaries":[{"binary_name":"libc-ares-dev","binary_version":"1.34.4-2.1ubuntu0.1"},{"binary_name":"libc-ares2","binary_version":"1.34.4-2.1ubuntu0.1"},{"binary_name":"libcares2","binary_version":"1.34.4-2.1ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2025/UBUNTU-CVE-2025-31498.json"}}],"schema_version":"1.7.3","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}