{"id":"UBUNTU-CVE-2026-4438","details":"Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C library version 2.34 to version 2.43 could result in an invalid DNS hostname being returned to the caller in violation of the DNS specification.","modified":"2026-07-27T21:00:19.875368266Z","published":"2026-03-20T20:16:00Z","related":["USN-8611-1"],"upstream":["CVE-2026-4438"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-4438"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-4438"},{"type":"REPORT","url":"https://www.openwall.com/lists/oss-security/2026/03/23/2"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8611-1"}],"affected":[{"package":{"name":"eglibc","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/eglibc?arch=source&distro=esm-infra-legacy%2Ftrusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.17-93ubuntu4","2.18-0ubuntu1","2.18-0ubuntu2","2.18-0ubuntu4","2.18-0ubuntu5","2.18-0ubuntu6","2.18-0ubuntu7","2.19-0ubuntu2","2.19-0ubuntu3","2.19-0ubuntu4","2.19-0ubuntu5","2.19-0ubuntu6","2.19-0ubuntu6.1","2.19-0ubuntu6.3","2.19-0ubuntu6.4","2.19-0ubuntu6.5","2.19-0ubuntu6.6","2.19-0ubuntu6.7","2.19-0ubuntu6.8","2.19-0ubuntu6.9","2.19-0ubuntu6.10","2.19-0ubuntu6.11","2.19-0ubuntu6.13","2.19-0ubuntu6.14","2.19-0ubuntu6.15","2.19-0ubuntu6.15+esm1","2.19-0ubuntu6.15+esm2","2.19-0ubuntu6.15+esm3","2.19-0ubuntu6.15+esm4"],"ecosystem_specific":{"binaries":[{"binary_name":"eglibc-source","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_name":"libc-bin","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_version":"2.19-0ubuntu6.15+esm4","binary_name":"libc-dev-bin"},{"binary_version":"2.19-0ubuntu6.15+esm4","binary_name":"libc6"},{"binary_name":"libc6-amd64","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_name":"libc6-armel","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_version":"2.19-0ubuntu6.15+esm4","binary_name":"libc6-dev-amd64"},{"binary_name":"libc6-dev-armel","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_name":"libc6-dev-i386","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_version":"2.19-0ubuntu6.15+esm4","binary_name":"libc6-dev-x32"},{"binary_version":"2.19-0ubuntu6.15+esm4","binary_name":"libc6-i386"},{"binary_name":"libc6-pic","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_version":"2.19-0ubuntu6.15+esm4","binary_name":"libc6-prof"},{"binary_version":"2.19-0ubuntu6.15+esm4","binary_name":"libc6-x32"},{"binary_name":"multiarch-support","binary_version":"2.19-0ubuntu6.15+esm4"},{"binary_name":"nscd","binary_version":"2.19-0ubuntu6.15+esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-4438.json"}},{"package":{"name":"glibc","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/glibc?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.39-0ubuntu8.8"}]}],"versions":["2.38-1ubuntu6","2.38-3ubuntu1","2.39-0ubuntu1","2.39-0ubuntu2","2.39-0ubuntu6","2.39-0ubuntu8","2.39-0ubuntu8.1","2.39-0ubuntu8.2","2.39-0ubuntu8.3","2.39-0ubuntu8.4","2.39-0ubuntu8.5","2.39-0ubuntu8.6","2.39-0ubuntu8.7"],"ecosystem_specific":{"binaries":[{"binary_version":"2.39-0ubuntu8.8","binary_name":"glibc-source"},{"binary_name":"libc-bin","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc-dev-bin","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc-devtools","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc6","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc6-amd64","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc6-dev-amd64","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc6-dev-i386","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc6-dev-s390","binary_version":"2.39-0ubuntu8.8"},{"binary_version":"2.39-0ubuntu8.8","binary_name":"libc6-dev-x32"},{"binary_name":"libc6-i386","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc6-s390","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"libc6-x32","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"locales","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"locales-all","binary_version":"2.39-0ubuntu8.8"},{"binary_name":"nscd","binary_version":"2.39-0ubuntu8.8"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-4438.json"}},{"package":{"name":"glibc","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/glibc?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.41-6ubuntu1","2.41-6ubuntu2","2.41-9ubuntu1","2.42-0ubuntu1","2.42-0ubuntu3","2.42-0ubuntu3.1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.42-0ubuntu3.1","binary_name":"glibc-source"},{"binary_name":"libc-bin","binary_version":"2.42-0ubuntu3.1"},{"binary_version":"2.42-0ubuntu3.1","binary_name":"libc-dev-bin"},{"binary_version":"2.42-0ubuntu3.1","binary_name":"libc-devtools"},{"binary_name":"libc6","binary_version":"2.42-0ubuntu3.1"},{"binary_name":"libc6-amd64","binary_version":"2.42-0ubuntu3.1"},{"binary_version":"2.42-0ubuntu3.1","binary_name":"libc6-dev-amd64"},{"binary_name":"libc6-dev-i386","binary_version":"2.42-0ubuntu3.1"},{"binary_version":"2.42-0ubuntu3.1","binary_name":"libc6-dev-x32"},{"binary_version":"2.42-0ubuntu3.1","binary_name":"libc6-i386"},{"binary_name":"libc6-x32","binary_version":"2.42-0ubuntu3.1"},{"binary_name":"locales","binary_version":"2.42-0ubuntu3.1"},{"binary_name":"locales-all","binary_version":"2.42-0ubuntu3.1"},{"binary_version":"2.42-0ubuntu3.1","binary_name":"nscd"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-4438.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}