Red Hat Enterprise Linux - util-linux: util-linux: TOCTOU in the mount program when applying post-mount ownership/mode changes

Ubuntu Linux - [Local Privilege Escalation via TOCTOU in mount(8) hook_owner.c chmod/chown]

ubuntu_linux USN-8702-1: Ubuntu 22.04 LTS / Ubuntu 24.04 LTS / Ubuntu 26.04 LTS / Ubuntu Pro Realtime 22.04 LTS / Ubuntu Pro Realtime 24.04 LTS : util-linux vulnerabilities (USN-8702-1)

The remote SUSE Linux SLES16 / SLES_SAP16 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:23870-1 advisory.

    - CVE-2026-13595: heap use-after-free in `libblkid` nested partition probing (bsc#1269583).
    - CVE-2026-27456: TOCTOU in the mount program when setting up loop devices (bsc#1261606).
    - CVE-2026-53612: local privilege escalation via TOCTOU in mount(8) hook_owner.c chmod/chown     (bsc#1268886).
    - CVE-2026-53613: local privilege escalation via TOCTOU in mount(8) - Target Path Redirection     (bsc#1268886).
    - CVE-2026-53614: local privilege escalation via LIBMOUNT_FORCE_MOUNT2 Environment Variable -     nosuid/noexec       Bypass in SUID mount(8) (bsc#1268886).
    - CVE-2026-76642: failed external mount helper triggers privileged `X-mount` post-hooks, which enables     local privilege       escalation (bsc#1278349).
    - CVE-2026-78408: `nsenter --join-cgroup` leaks root `cgroup` migration authority, which allows for     migration or       termination of root processes (bsc#1278348).
    - CVE-2026-78410: restricted `bind` mounts do not pin the source, which allows for     `X-mount.owner`/`group`/`mode`       redirection (bsc#1278347).

    Changes for util-linux:

    - lib/fileutils: add ul_openat_resolve() openat2 wrapper (bsc#1275441)
    - lib/fileutils: fix RESOLVE_NO_SYMLINKS fallback value
    - lib/fileutils: fix unused parameter warnings without SYS_openat2
    - libmount: add missing fileutils.h include to hook_idmap.c
    - libmount: add mnt_open_tree() helper for safe tree opening
    - libmount: pin source path with openat2() for restricted users      (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: restrict source path canonicalization for non-root      users (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: skip post-mount hooks after failed mount helper      (bsc#1275441, bsc#1278349, CVE-2026-76642)
    - libmount: use USE_LIBMOUNT_MOUNTFD_SUPPORT for idmap hook
    - nsenter: close cgroup.procs fd after join to prevent authority      leak (bsc#1275441, bsc#1278348, CVE-2026-78408)
    - nsenter, unshare: add O_CLOEXEC to all open() calls (bsc#1275441,      bsc#1278348, CVE-2026-78408)
    - wall, write: sanitize hostname in banner header (bsc#1275441)
    - Add missing function. (bsc#1275441)
    - ipcutils: Prevent using uninitialized variable (bsc#1268886)
    - BREAKING CHANGE:
     Paths must always be canonicalized for unprivileged users to      ensure safe target resolution. X-mount.nocanonicalize is ignored      for them.
    - INCOMAPTIBLE CHANGE (linux < 6.15):
     X-mount.subdir: The safe detached subdirectory is no more      supported for unprivileged users for safety reasons.
    - liblastlog2: Wait on busy SQLite connections (bsc#1268886).
    - libmount: Fix subvolid buffer overflow in get_btrfs_fs_root      (bsc#1268886).
    - libblkid: Fix use-after-free in nested partition probing      (bsc#1269583, bsc#1268886, CVE-2026-13595)
    - libmount: fix SUID bypass via LIBMOUNT_FORCE_MOUNT2 and legacy      mount path (bsc#1268886, CVE-2026-53614, GHSA-67r7-8m5w-22wx).
    - fileutils: add ul_open_no_symlinks() needed by other patches      (bsc#1268886).
    - libmount: add fd_target to context for TOCTOU race condition      prevention (bsc#1268886, CVE-2026-53613, GHSA-8gj5-72r3-428g).
    - libmount: ignore X-mount.nocanonicalize for restricted users
    - libmount: use fd-based fchownat/chmod in hook_owner (bsc#1268886,      CVE-2026-53612, GHSA-g8wm-75wr-g2vh).
    - libmount: restrict X-mount.subdir for non-root (bsc#1268886).
    - libmount: use fd_target in hook_idmap for move_mount()
    - libmount: add mount ID verification and man page TOCTOU note
    - loopdev: use openat2(RESOLVE_NO_SYMLINKS) for backing file      (bsc#1268886#c2, bsc#1261606).
    - Ignore pam-config error that prevents update failure if common*      pam configuration is not symlink to common-*-pc (bsc#1270219).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote openSUSE 16 host has packages installed that are affected by multiple vulnerabilities as referenced in the openSUSE-SU-2026:21905-1 advisory.

    - CVE-2026-13595: heap use-after-free in `libblkid` nested partition probing (bsc#1269583).
    - CVE-2026-27456: TOCTOU in the mount program when setting up loop devices (bsc#1261606).
    - CVE-2026-53612: local privilege escalation via TOCTOU in mount(8) hook_owner.c chmod/chown     (bsc#1268886).
    - CVE-2026-53613: local privilege escalation via TOCTOU in mount(8) - Target Path Redirection     (bsc#1268886).
    - CVE-2026-53614: local privilege escalation via LIBMOUNT_FORCE_MOUNT2 Environment Variable -     nosuid/noexec       Bypass in SUID mount(8) (bsc#1268886).
    - CVE-2026-76642: failed external mount helper triggers privileged `X-mount` post-hooks, which enables     local privilege       escalation (bsc#1278349).
    - CVE-2026-78408: `nsenter --join-cgroup` leaks root `cgroup` migration authority, which allows for     migration or       termination of root processes (bsc#1278348).
    - CVE-2026-78410: restricted `bind` mounts do not pin the source, which allows for     `X-mount.owner`/`group`/`mode`       redirection (bsc#1278347).

    Changes for util-linux:

    - lib/fileutils: add ul_openat_resolve() openat2 wrapper (bsc#1275441)
    - lib/fileutils: fix RESOLVE_NO_SYMLINKS fallback value
    - lib/fileutils: fix unused parameter warnings without SYS_openat2
    - libmount: add missing fileutils.h include to hook_idmap.c
    - libmount: add mnt_open_tree() helper for safe tree opening
    - libmount: pin source path with openat2() for restricted users      (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: restrict source path canonicalization for non-root      users (bsc#1275441, bsc#1278347, CVE-2026-78410)
    - libmount: skip post-mount hooks after failed mount helper      (bsc#1275441, bsc#1278349, CVE-2026-76642)
    - libmount: use USE_LIBMOUNT_MOUNTFD_SUPPORT for idmap hook
    - nsenter: close cgroup.procs fd after join to prevent authority      leak (bsc#1275441, bsc#1278348, CVE-2026-78408)
    - nsenter, unshare: add O_CLOEXEC to all open() calls (bsc#1275441,      bsc#1278348, CVE-2026-78408)
    - wall, write: sanitize hostname in banner header (bsc#1275441)
    - Add missing function. (bsc#1275441)
    - ipcutils: Prevent using uninitialized variable (bsc#1268886)
    - BREAKING CHANGE:
     Paths must always be canonicalized for unprivileged users to      ensure safe target resolution. X-mount.nocanonicalize is ignored      for them.
    - INCOMAPTIBLE CHANGE (linux < 6.15):
     X-mount.subdir: The safe detached subdirectory is no more      supported for unprivileged users for safety reasons.
    - liblastlog2: Wait on busy SQLite connections (bsc#1268886).
    - libmount: Fix subvolid buffer overflow in get_btrfs_fs_root      (bsc#1268886).
    - libblkid: Fix use-after-free in nested partition probing      (bsc#1269583, bsc#1268886, CVE-2026-13595)
    - libmount: fix SUID bypass via LIBMOUNT_FORCE_MOUNT2 and legacy      mount path (bsc#1268886, CVE-2026-53614, GHSA-67r7-8m5w-22wx).
    - fileutils: add ul_open_no_symlinks() needed by other patches      (bsc#1268886).
    - libmount: add fd_target to context for TOCTOU race condition      prevention (bsc#1268886, CVE-2026-53613, GHSA-8gj5-72r3-428g).
    - libmount: ignore X-mount.nocanonicalize for restricted users
    - libmount: use fd-based fchownat/chmod in hook_owner (bsc#1268886,      CVE-2026-53612, GHSA-g8wm-75wr-g2vh).
    - libmount: restrict X-mount.subdir for non-root (bsc#1268886).
    - libmount: use fd_target in hook_idmap for move_mount()
    - libmount: add mount ID verification and man page TOCTOU note
    - loopdev: use openat2(RESOLVE_NO_SYMLINKS) for backing file      (bsc#1268886#c2, bsc#1261606).
    - Ignore pam-config error that prevents update failure if common*      pam configuration is not symlink to common-*-pc (bsc#1270219).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLED15 / SLED_SAP15 / SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:3684-1 advisory.

    - CVE-2026-13595: heap use-after-free read in `libblkid` nested partition probing (bsc#1269583).
    - CVE-2026-27456: TOCTOU race condition in the mount program when setting up loop devices (bsc#1261606).
    - Several security issues in releases prior to v2.42.2 and v2.41.5 (bsc#1268886).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote SUSE Linux SLES15 / SLES_SAP15 host has packages installed that are affected by multiple vulnerabilities as referenced in the SUSE-SU-2026:3685-1 advisory.

    - CVE-2026-13595: heap use-after-free read in `libblkid` nested partition probing (bsc#1269583).
    - CVE-2026-27456: TOCTOU race condition in the mount program when setting up loop devices (bsc#1261606).
    - Several security issues in releases prior to v2.42.2 and v2.41.5 (bsc#1268886).

Tenable has extracted the preceding description block directly from the SUSE security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Debian 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6442 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6442-1                   security@debian.org     https://www.debian.org/security/                     Salvatore Bonaccorso     August 14, 2026                       https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : util-linux     CVE ID         : CVE-2026-13595 CVE-2026-27456 CVE-2026-53612 CVE-2026-53613                      CVE-2026-53614     Debian Bug     : 1140194 1140195 1140196

    Several vulnerabilities were discovered in util-linux which could result     in privilege escalation.

    For the stable distribution (trixie), these problems have been fixed in     version 2.41.5-0+deb13u1.

    We recommend that you upgrade your util-linux packages.

    For the detailed security status of util-linux please refer to its     security tracker page at:
    https://security-tracker.debian.org/tracker/util-linux

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 43 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-a7ff7017ee advisory.

    upstream upgrade with security fixes:

      - CVE-2026-53612 - libmount: TOCTOU attack via ancestor directory swap during mount
      - CVE-2026-53613 - libmount: SUID bypass via LIBMOUNT_FORCE_MOUNT2 and legacy mount path
      - CVE-2026-53614 - libmount: fd_target TOCTOU prevention


Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The remote Fedora 44 host has a package installed that is affected by multiple vulnerabilities as referenced in the FEDORA-2026-c70cb96ff1 advisory.

    upstream upgrade with security fixes:

      - CVE-2026-53612 - libmount: TOCTOU attack via ancestor directory swap during mount
      - CVE-2026-53613 - libmount: SUID bypass via LIBMOUNT_FORCE_MOUNT2 and legacy mount path
      - CVE-2026-53614 - libmount: fd_target TOCTOU prevention


Tenable has extracted the preceding description block directly from the Fedora security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - upstream upgrade with security fixes:    - CVE-2026-53612 - libmount: TOCTOU attack via ancestor directory     swap during mount   - CVE-2026-53613 - libmount: SUID bypass via LIBMOUNT_FORCE_MOUNT2 and legacy mount     path   - CVE-2026-53614 - libmount: fd_target TOCTOU prevention  (CVE-2026-53612)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
350831	SUSE SLES16: lastlog2 / libblkid-devel / libblkid-devel-static / libblkid1 / etc (SUSE-SU-2026:23870-1)	Nessus	SuSE Local Security Checks	Local	high
350149	openSUSE 16: lastlog2 / libblkid-devel / libblkid-devel-static / libblkid1 / etc (openSUSE-SU-2026:21905-1)	Nessus	SuSE Local Security Checks	Local	high
339736	SUSE SLED15: libblkid-devel / libblkid-devel-static / libblkid1 / etc (SUSE-SU-2026:3684-1)	Nessus	SuSE Local Security Checks	Local	medium
339726	SUSE SLES15: libblkid-devel / libblkid-devel-static / libblkid1 / etc (SUSE-SU-2026:3685-1)	Nessus	SuSE Local Security Checks	Local	medium
335429	Debian dsa-6442 : bsdextrautils - security update	Nessus	Debian Local Security Checks	Local	medium
323123	Fedora 43 : util-linux (2026-a7ff7017ee)	Nessus	Fedora Local Security Checks	Local	high
321735	Fedora 44 : util-linux (2026-c70cb96ff1)	Nessus	Fedora Local Security Checks	Local	high
321413	Linux Distros Unpatched Vulnerability : CVE-2026-53612	Nessus	Misc.	Local	high

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