{"id":"USN-4966-2","summary":"libx11 vulnerability","details":"USN-4966-1 fixed a vulnerability in libx11. This update provides\nthe corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.\n\nOriginal advisory details:\n\n It was discovered that libx11 incorrectly validated certain parameter\n lengths. A remote attacker could possibly use this issue to trick libx11\n into emitting extra X protocol requests.\n","modified":"2026-05-20T16:03:07.708382761Z","published":"2021-05-25T19:02:59Z","related":["UBUNTU-CVE-2021-31535"],"upstream":["CVE-2021-31535","UBUNTU-CVE-2021-31535"],"references":[{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-4966-2"},{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2021-31535"}],"affected":[{"package":{"name":"libx11","ecosystem":"Ubuntu:Pro:14.04:LTS","purl":"pkg:deb/ubuntu/libx11?arch=source&distro=trusty%2Fesm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2:1.6.2-1ubuntu2.1+esm2"}]}],"versions":["2:1.6.1-1ubuntu1","2:1.6.1-1ubuntu2","2:1.6.2-1ubuntu1","2:1.6.2-1ubuntu2","2:1.6.2-1ubuntu2.1","2:1.6.2-1ubuntu2.1+esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"libx11-6","binary_version":"2:1.6.2-1ubuntu2.1+esm2"},{"binary_name":"libx11-data","binary_version":"2:1.6.2-1ubuntu2.1+esm2"},{"binary_name":"libx11-xcb1","binary_version":"2:1.6.2-1ubuntu2.1+esm2"}],"availability":"Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-4966-2.json","cves_map":{"cves":[{"severity":[{"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":"medium"}],"id":"CVE-2021-31535"}],"ecosystem":"Ubuntu:Pro:14.04:LTS"}}},{"package":{"name":"libx11","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/libx11?arch=source&distro=esm-apps%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2:1.6.3-1ubuntu2.2+esm1"}]}],"versions":["2:1.6.3-1ubuntu2","2:1.6.3-1ubuntu2.1","2:1.6.3-1ubuntu2.2"],"ecosystem_specific":{"binaries":[{"binary_name":"libx11-6","binary_version":"2:1.6.3-1ubuntu2.2+esm1"},{"binary_name":"libx11-data","binary_version":"2:1.6.3-1ubuntu2.2+esm1"},{"binary_name":"libx11-xcb1","binary_version":"2:1.6.3-1ubuntu2.2+esm1"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-4966-2.json","cves_map":{"cves":[],"ecosystem":"Ubuntu:Pro:16.04:LTS"}}}],"schema_version":"1.7.5"}