{"id":"UBUNTU-CVE-2026-27456","details":"util-linux is a random collection of Linux utilities. Prior to version 2.41.4, a TOCTOU (Time-of-Check-Time-of-Use) vulnerability has been identified in the SUID binary /usr/bin/mount from util-linux. The mount binary, when setting up loop devices, validates the source file path with user privileges via fork() + setuid() + realpath(), but subsequently re-canonicalizes and opens it with root privileges (euid=0) without verifying that the path has not been replaced between both operations. Neither O_NOFOLLOW, nor inode comparison, nor post-open fstat() are employed. This allows a local unprivileged user to replace the source file with a symlink pointing to any root-owned file or device during the race window, causing the SUID binary to open and mount it as root. Exploitation requires an /etc/fstab entry with user,loop options whose path points to a directory where the attacker has write permission, and that /usr/bin/mount has the SUID bit set (the default configuration on virtually all Linux distributions). The impact is unauthorized read access to root-protected files and block devices, including backup images, disk volumes, and any file containing a valid filesystem. This issue has been patched in version 2.41.4.","modified":"2026-08-31T22:15:15.467088947Z","published":"2026-04-03T22:16:00Z","related":["USN-8702-1"],"upstream":["CVE-2026-27456"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-27456"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-27456"},{"type":"REPORT","url":"https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"},{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8702-1"}],"affected":[{"package":{"name":"util-linux","ecosystem":"Ubuntu:14.04:LTS","purl":"pkg:deb/ubuntu/util-linux?arch=source&distro=trusty"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.20.1-5.1ubuntu9","2.20.1-5.1ubuntu10","2.20.1-5.1ubuntu11","2.20.1-5.1ubuntu12","2.20.1-5.1ubuntu13","2.20.1-5.1ubuntu14","2.20.1-5.1ubuntu15","2.20.1-5.1ubuntu16","2.20.1-5.1ubuntu17","2.20.1-5.1ubuntu18","2.20.1-5.1ubuntu19","2.20.1-5.1ubuntu20","2.20.1-5.1ubuntu20.1","2.20.1-5.1ubuntu20.2","2.20.1-5.1ubuntu20.3","2.20.1-5.1ubuntu20.4","2.20.1-5.1ubuntu20.6","2.20.1-5.1ubuntu20.7","2.20.1-5.1ubuntu20.9"],"ecosystem_specific":{"binaries":[{"binary_version":"1:2.20.1-5.1ubuntu20.9","binary_name":"bsdutils"},{"binary_name":"libblkid1","binary_version":"2.20.1-5.1ubuntu20.9"},{"binary_name":"libmount1","binary_version":"2.20.1-5.1ubuntu20.9"},{"binary_version":"2.20.1-5.1ubuntu20.9","binary_name":"libuuid1"},{"binary_version":"2.20.1-5.1ubuntu20.9","binary_name":"mount"},{"binary_version":"2.20.1-5.1ubuntu20.9","binary_name":"util-linux"},{"binary_name":"util-linux-locales","binary_version":"2.20.1-5.1ubuntu20.9"},{"binary_version":"2.20.1-5.1ubuntu20.9","binary_name":"uuid-runtime"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27456.json"}},{"package":{"name":"util-linux","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.26.2-6ubuntu3","2.27-3ubuntu1","2.27.1-1ubuntu2","2.27.1-1ubuntu3","2.27.1-1ubuntu4","2.27.1-3ubuntu1","2.27.1-4ubuntu1","2.27.1-6ubuntu1","2.27.1-6ubuntu2","2.27.1-6ubuntu3","2.27.1-6ubuntu3.1","2.27.1-6ubuntu3.2","2.27.1-6ubuntu3.3","2.27.1-6ubuntu3.4","2.27.1-6ubuntu3.6","2.27.1-6ubuntu3.7","2.27.1-6ubuntu3.8","2.27.1-6ubuntu3.9","2.27.1-6ubuntu3.10","2.27.1-6ubuntu3.10+esm2"],"ecosystem_specific":{"binaries":[{"binary_name":"bsdutils","binary_version":"1:2.27.1-6ubuntu3.10+esm2"},{"binary_name":"libblkid1","binary_version":"2.27.1-6ubuntu3.10+esm2"},{"binary_name":"libfdisk1","binary_version":"2.27.1-6ubuntu3.10+esm2"},{"binary_name":"libmount1","binary_version":"2.27.1-6ubuntu3.10+esm2"},{"binary_version":"2.27.1-6ubuntu3.10+esm2","binary_name":"libsmartcols1"},{"binary_name":"libuuid1","binary_version":"2.27.1-6ubuntu3.10+esm2"},{"binary_name":"mount","binary_version":"2.27.1-6ubuntu3.10+esm2"},{"binary_name":"util-linux","binary_version":"2.27.1-6ubuntu3.10+esm2"},{"binary_name":"util-linux-locales","binary_version":"2.27.1-6ubuntu3.10+esm2"},{"binary_version":"2.27.1-6ubuntu3.10+esm2","binary_name":"uuid-runtime"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27456.json"}},{"package":{"name":"util-linux","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/util-linux?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.30.1-0ubuntu4","2.30.2-0.1ubuntu1","2.30.2-0.1ubuntu2","2.30.2-0.1ubuntu3","2.31.1-0.4ubuntu2","2.31.1-0.4ubuntu3","2.31.1-0.4ubuntu3.1","2.31.1-0.4ubuntu3.2","2.31.1-0.4ubuntu3.3","2.31.1-0.4ubuntu3.4","2.31.1-0.4ubuntu3.5","2.31.1-0.4ubuntu3.6","2.31.1-0.4ubuntu3.7"],"ecosystem_specific":{"binaries":[{"binary_version":"1:2.31.1-0.4ubuntu3.7","binary_name":"bsdutils"},{"binary_name":"fdisk","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_name":"libblkid1","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_name":"libfdisk1","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_name":"libmount1","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_name":"libsmartcols1","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_version":"2.31.1-0.4ubuntu3.7","binary_name":"libuuid1"},{"binary_version":"2.31.1-0.4ubuntu3.7","binary_name":"mount"},{"binary_name":"rfkill","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_name":"setpriv","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_version":"2.31.1-0.4ubuntu3.7","binary_name":"util-linux"},{"binary_name":"util-linux-locales","binary_version":"2.31.1-0.4ubuntu3.7"},{"binary_name":"uuid-runtime","binary_version":"2.31.1-0.4ubuntu3.7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-27456.json"}},{"package":{"name":"util-linux","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra%2Ffocal"},"ranges":[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