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.

The remote Fedora 44 host has a package installed that is affected by a vulnerability as referenced in the FEDORA-2026-67cf3d6cca advisory.

    upstream update, fixes security-related bugs

    CVE-2026-27456 - mount(8) TOCTOU symlink attack via loop device. The SUID mount follows symlinks when     resolving loop backing file paths. On systems where non-root users are permitted to mount loop devices     (via 'user' option in fstab), this allows access to arbitrary files.

    CWE-190 - Integer overflow in libblkid parse_dos_extended(). A crafted MBR disk image can cause uint32_t     wraparound in EBR chain processing, causing reported partitions to not match the on-disk layout. Tools     like udisks may then register a partition at logical sector 0.

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

Note that Nessus has not tested for this issue 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 a vulnerability as referenced in the FEDORA-2026-840b40ef4c advisory.

    upstream update, fixes security-related bugs

     CVE-2026-27456 - mount(8) TOCTOU symlink attack via loop device.
       The SUID mount follows symlinks when resolving loop backing file        paths. On systems where non-root users are permitted to mount loop        devices (via 'user' option in fstab), this allows access to        arbitrary files.

     CWE-190 - Integer overflow in libblkid parse_dos_extended().
       A crafted MBR disk image can cause uint32_t wraparound in EBR        chain processing, causing reported partitions to not match the        on-disk layout. Tools like udisks may then register a partition        at logical sector 0.


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

Note that Nessus has not tested for this issue 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.

  - 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. (CVE-2026-27456)

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

ID	Name	Product	Family	Severity
310699	Fedora 44 : util-linux (2026-67cf3d6cca)	Nessus	Fedora Local Security Checks	medium
307050	Fedora 43 : util-linux (2026-840b40ef4c)	Nessus	Fedora Local Security Checks	medium
304773	Linux Distros Unpatched Vulnerability : CVE-2026-27456	Nessus	Misc.	medium

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CVE-2026-27456

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