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CVE-2026-27456

CVE-2026-27456 · util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup

This page contains facts from public vulnerability sources. Check the original advisory before updating.

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.

CVSS 4.7 · Medium · EPSS 0.1% · Fix available

Published
Updated

Stack: system

Affected products and versions

  • util-linux

    Versions
    • < 2.41.4: Affected

    No fix published

  • util-linux Debian:12

    Versions
    • 2.38.1-5
    • 2.38.1-5+deb12u1
    • 2.38.1-5+deb12u2
    • 2.38.1-5+deb12u3
    • 2.38.1-5+loong64
    • 2.38.1-6
    • 2.39.1-1
    • 2.39.1-2
    • 2.39.1-3
    • 2.39.1-4
    • 2.39.2-1
    • 2.39.2-2
    • 2.39.2-2.1
    • 2.39.2-2.2
    • 2.39.2-3
    • 2.39.2-4
    • 2.39.2-5
    • 2.39.2-6
    • 2.39.3-1
    • 2.39.3-10
    • 2.39.3-11
    • 2.39.3-2
    • 2.39.3-3
    • 2.39.3-4
    • 2.39.3-5
    • 2.39.3-6
    • 2.39.3-6.1
    • 2.39.3-6.1~exp1
    • 2.39.3-7
    • 2.39.3-8
    • 2.39.3-9
    • 2.40-1
    • 2.40-2
    • 2.40-3
    • 2.40-4
    • 2.40-5
    • 2.40-6
    • 2.40-7
    • 2.40-8
    • 2.40.1-1
    • 2.40.1-2
    • 2.40.1-3
    • 2.40.1-4
    • 2.40.1-4+hurd.1
    • 2.40.1-6
    • 2.40.1-7
    • 2.40.1-8
    • 2.40.1-8.1
    • 2.40.1-9
    • 2.40.2-1
    • 2.40.2-10
    • 2.40.2-11
    • 2.40.2-12
    • 2.40.2-12+hurd.1
    • 2.40.2-13
    • 2.40.2-14
    • 2.40.2-2
    • 2.40.2-3
    • 2.40.2-4
    • 2.40.2-5
    • 2.40.2-6
    • 2.40.2-7
    • 2.40.2-8
    • 2.40.2-9
    • 2.40.3-1
    • 2.40.4-1
    • 2.40.4-2
    • 2.40.4-3
    • 2.40.4-4
    • 2.40.4-5
    • 2.40~rc2-1
    • 2.40~rc2-2
    • 2.40~rc2-3
    • 2.40~rc2-4
    • 2.40~rc2-5
    • 2.40~rc2-6
    • 2.40~rc2-7
    • 2.40~rc2-8
    • 2.41-1
    • 2.41-2
    • 2.41-3
    • 2.41-4
    • 2.41-5
    • 2.41.1-1
    • 2.41.1-2
    • 2.41.1-3
    • 2.41.1-4
    • 2.41.2-1
    • 2.41.2-2
    • 2.41.2-3
    • 2.41.2-4
    • 2.41.3-1
    • 2.41.3-2
    • 2.41.3-3
    • 2.41.3-4
    • 2.41~rc1-1
    • 2.41~rc1-2
    • 2.41~rc2-1
    • 2.42-1
    • 2.42-2
    • 2.42-3
    • 2.42-4
    • 2.42-5
    • 2.42-6
    • 2.42.1-1
    • 2.42.1-2
    • 2.42.1-3
    • 2.42.1-4
    • 2.42.1-5
    • 2.42.1-6
    • 2.42.2-1
    • 2.42.2-2
    • 2.42.2-3
    • 2.42.2-4
    • 2.42.3-1
    • 2.42.4-1
    • 2.42~rc1-1
    • 2.42~rc1-2
    • 2.42~rc1-3
    • 2.42~rc2-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • util-linux Debian:13

    Versions
    • 2.41-5
    • 2.41.1-1
    • 2.41.1-2
    • 2.41.1-3
    • 2.41.1-4
    • 2.41.2-1
    • 2.41.2-2
    • 2.41.2-3
    • 2.41.2-4
    • 2.41.3-1
    • 2.41.3-2
    • 2.41.3-3
    • 2.41.3-4
    Affected ranges
    • ECOSYSTEM: < 2.41.5-0+deb13u1

    Update to 2.41.5-0+deb13u1

  • util-linux Debian:14

    Versions
    • 2.41-5
    • 2.41.1-1
    • 2.41.1-2
    • 2.41.1-3
    • 2.41.1-4
    • 2.41.2-1
    • 2.41.2-2
    • 2.41.2-3
    • 2.41.2-4
    • 2.41.3-1
    • 2.41.3-2
    • 2.41.3-3
    • 2.41.3-4
    • 2.42~rc1-1
    • 2.42~rc1-2
    • 2.42~rc1-3
    • 2.42~rc2-1
    Affected ranges
    • ECOSYSTEM: < 2.42-1

    Update to 2.42-1

  • util-linux Ubuntu:14.04:LTS

    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
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • util-linux Ubuntu:Pro:16.04:LTS

    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
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • util-linux Ubuntu:18.04:LTS

    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
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • util-linux Ubuntu:Pro:20.04:LTS

    Versions
    • 2.34-0.1ubuntu2
    • 2.34-0.1ubuntu4
    • 2.34-0.1ubuntu5
    • 2.34-0.1ubuntu6
    • 2.34-0.1ubuntu7
    • 2.34-0.1ubuntu8
    • 2.34-0.1ubuntu9
    • 2.34-0.1ubuntu9.1
    • 2.34-0.1ubuntu9.3
    • 2.34-0.1ubuntu9.4
    • 2.34-0.1ubuntu9.5
    • 2.34-0.1ubuntu9.6
    • 2.34-0.1ubuntu9.6+esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • util-linux Ubuntu:22.04:LTS

    Versions
    • 2.36.1-8ubuntu1
    • 2.37.2-4ubuntu1
    • 2.37.2-4ubuntu2
    • 2.37.2-4ubuntu3
    • 2.37.2-4ubuntu3.3
    • 2.37.2-4ubuntu3.4
    • 2.37.2-4ubuntu3.5
    Affected ranges
    • ECOSYSTEM: < 2.37.2-4ubuntu3.6

    Update to 2.37.2-4ubuntu3.6

  • util-linux Ubuntu:24.04:LTS

    Versions
    • 2.39.1-4ubuntu2
    • 2.39.2-6ubuntu1
    • 2.39.3-6ubuntu2
    • 2.39.3-9ubuntu2
    • 2.39.3-9ubuntu4
    • 2.39.3-9ubuntu6
    • 2.39.3-9ubuntu6.1
    • 2.39.3-9ubuntu6.2
    • 2.39.3-9ubuntu6.3
    • 2.39.3-9ubuntu6.4
    • 2.39.3-9ubuntu6.5
    Affected ranges
    • ECOSYSTEM: < 2.39.3-9ubuntu6.6

    Update to 2.39.3-9ubuntu6.6

  • util-linux Ubuntu:25.10

    Versions
    • 2.40.2-14ubuntu1
    • 2.41-4ubuntu2
    • 2.41-4ubuntu3
    • 2.41-4ubuntu4
    • 2.41-4ubuntu4.1
    • 2.41-4ubuntu4.2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • util-linux Ubuntu:26.10

    Versions
    • 2.41.3-3ubuntu2
    • 2.42.2-1ubuntu2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • util-linux Ubuntu:26.04:LTS

    Versions
    • 2.41-4ubuntu4
    • 2.41.2-4ubuntu1
    • 2.41.2-4ubuntu2
    • 2.41.2-4ubuntu3
    • 2.41.3-3ubuntu1
    • 2.41.3-3ubuntu2
    Affected ranges
    • ECOSYSTEM: < 2.41.3-3ubuntu2.2

    Update to 2.41.3-3ubuntu2.2

Original sources

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