{"id":"CVE-2026-27456","summary":"util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup","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.","aliases":["GHSA-qq4x-vfq4-9h9g"],"modified":"2026-07-15T01:48:58.728785111Z","published":"2026-04-03T21:23:00.984Z","related":["SUSE-SU-2026:1962-1","SUSE-SU-2026:21727-1","SUSE-SU-2026:21742-1","SUSE-SU-2026:22260-1","SUSE-SU-2026:22332-1","SUSE-SU-2026:2485-1","SUSE-SU-2026:2492-1","SUSE-SU-2026:2653-1","openSUSE-SU-2026:10736-1","openSUSE-SU-2026:21028-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27456.json","cna_assigner":"GitHub_M","cwe_ids":["CWE-269","CWE-367","CWE-59"]},"references":[{"type":"WEB","url":"https://github.com/util-linux/util-linux/releases/tag/v2.41.4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27456.json"},{"type":"ADVISORY","url":"https://github.com/util-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9g"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27456"},{"type":"FIX","url":"https://github.com/util-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3162fc4"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/util-linux/util-linux","events":[{"introduced":"0"},{"fixed":"e147e16fa9a9d3b3ad5968bf42280966ac3a8529"},{"fixed":"5e390467b26a3cf3fecc04e1a0d482dff3162fc4"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"2.41.4"}],"source":["CPE_RANGE","REFERENCES"],"cpe":"cpe:2.3:a:kernel:util-linux:*:*:*:*:*:*:*:*"}}],"versions":["v2.43-devel","v2.41.3","v2.41.2","v2.41.2-rc1","v2.41.1","v2.41","v2.41-rc2","v2.41-rc1","v2.42-start","v2.41-start","v2.41-devel","v2.40-rc1","v2.39","v2.39-rc3","v2.39-rc2","v2.39-rc1","v2.38","v2.38-rc4","v2.38-rc3","v2.38-rc2","v2.38-rc1","v2.37","v2.37-rc2","v2.37-rc1","v2.36","v2.36-rc2","v2.36-rc1","v2.35","v2.35-rc2","v2.35-rc1","v2.34","v2.34-rc2","v2.34-rc1","v2.33","v2.33-rc2","v2.33-rc1","v2.32","v2.32-rc2","v2.32-rc1","v2.31","v2.31-rc2","v2.31-rc1","v2.30","v2.30-rc2","v2.30-rc1","v2.29","v2.29-rc2","v2.29-rc1","v2.28","v2.28-rc2","v2.28-rc1","v2.27","v2.27-rc2","v2.27-rc1","v2.26","v2.26-rc2","v2.26-rc1","v2.25","v2.25-rc2","v2.25-rc1","v2.24","v2.24-rc2","v2.24-rc1","v2.23","v2.23-rc2","v2.23-rc1","v2.22","v2.22-rc2","v2.22-rc1","v2.21","v2.21-rc2","v2.21-rc1","v2.20","v2.20-rc2","v2.20-rc1","v2.19","v2.19-rc3","v2.19-rc2","v2.19-rc1","v2.18","v2.18-rc2","v2.18-rc1","v2.17","v2.17-rc3","v2.17-rc2","v2.17-rc1","v2.16","v2.16-rc2","v2.16-rc1","v2.15","v2.15-rc2","v2.15-rc1","v2.14","v2.14-rc3","v2.14-rc2","v2.14-rc1","v2.13","v2.13-rc3","v2.13-rc2","v2.13-rc1","v2.13-pre7","v2.13-pre6","v2.13-pre5","v2.13-pre4","v2.13-pre3","v2.13-pre2","v2.13-pre1","v2.12r","v2.12r-pre1","v2.12q","v2.12q-pre2","v2.12q-pre1","v2.12p","v2.12o","v2.12m","v2.12l","v2.12k","v2.12j","v2.12i","v2.12h","v2.12d","v2.12b","v2.12a","v2.12pre","v2.12","v2.11y","v2.11x","v2.11w","v2.11v","v2.11u","v2.11t","v2.11r","v2.11q","v2.11o","v2.11n","v2.11m","v2.11f","v2.11b","v2.10s","v2.10m","v2.10f","v2.9v","v2.9i","v2.8","v2.7.1","v2.5","v2.2"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-27456.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N"}]}