{"id":"UBUNTU-CVE-2026-33630","details":"c-ares is an asynchronous resolver library. From ver 1.32.3 until 1.34.7, a use-after-free / double-free in c-ares' query-completion handling. The same flaw — a query's callback being invoked while the query is still linked in the channel's internal lookup structures — is present at multiple points in the resend/finish path (timeout handling, response handling, and query dispatch). If the query, or for ares_getaddrinfo() the owning host_query, is freed as a side effect of that callback, it is then accessed and/or freed a second time. This vulnerability is fixed in ver 1.34.7.","modified":"2026-09-16T14:01:43.885911376Z","published":"2026-09-03T19:17:00Z","upstream":["CVE-2026-33630"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-33630"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-33630"},{"type":"REPORT","url":"https://www.openwall.com/lists/oss-security/2026/07/06/8"},{"type":"REPORT","url":"https://github.com/c-ares/c-ares/security/advisories/GHSA-6wfj-rwm7-3542"}],"affected":[{"package":{"name":"c-ares","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/c-ares?arch=source&distro=esm-infra%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.0-2","1.10.0-3","1.10.0-3ubuntu0.1","1.10.0-3ubuntu0.2","1.10.0-3ubuntu0.2+esm1","1.10.0-3ubuntu0.2+esm2","1.10.0-3ubuntu0.2+esm3"],"ecosystem_specific":{"binaries":[{"binary_version":"1.10.0-3ubuntu0.2+esm3","binary_name":"libc-ares2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33630.json"}},{"package":{"name":"c-ares","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/c-ares?arch=source&distro=esm-infra%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.13.0-2","1.13.0-3","1.14.0-1","1.14.0-1ubuntu0.1","1.14.0-1ubuntu0.2","1.14.0-1ubuntu0.2+esm1","1.14.0-1ubuntu0.2+esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"libc-ares2","binary_version":"1.14.0-1ubuntu0.2+esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33630.json"}},{"package":{"name":"c-ares","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/c-ares?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.15.0-1build1","1.15.0-1ubuntu0.1","1.15.0-1ubuntu0.2","1.15.0-1ubuntu0.3","1.15.0-1ubuntu0.4","1.15.0-1ubuntu0.5"],"ecosystem_specific":{"binaries":[{"binary_name":"libc-ares2","binary_version":"1.15.0-1ubuntu0.5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33630.json"}},{"package":{"name":"c-ares","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/c-ares?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.17.1-1ubuntu1","1.18.1-1","1.18.1-1build1","1.18.1-1ubuntu0.22.04.1","1.18.1-1ubuntu0.22.04.2","1.18.1-1ubuntu0.22.04.3"],"ecosystem_specific":{"binaries":[{"binary_name":"libc-ares2","binary_version":"1.18.1-1ubuntu0.22.04.3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33630.json"}},{"package":{"name":"c-ares","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/c-ares?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.19.1-3","1.20.1-1","1.26.0-1","1.27.0-1","1.27.0-1.0ubuntu1"],"ecosystem_specific":{"binaries":[{"binary_name":"libcares2","binary_version":"1.27.0-1.0ubuntu1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33630.json"}},{"package":{"name":"c-ares","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/c-ares?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.34.4-2.1","1.34.5-1","1.34.5-1ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"libc-ares2","binary_version":"1.34.5-1ubuntu0.1"},{"binary_name":"libcares2","binary_version":"1.34.5-1ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33630.json"}},{"package":{"name":"c-ares","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/c-ares?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.34.5-1","1.34.6-1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.34.6-1","binary_name":"libc-ares2"},{"binary_name":"libcares2","binary_version":"1.34.6-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33630.json"}}],"schema_version":"1.9.0","severity":[{"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"}]}