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CVE-2026-78409VulnerabilityPublished Updated

Util linux: The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured

Affects util-linuxSource GCVE Database

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Authoritative record:CVE-2026-78409· High 7.0

Not known to be exploited · CVSS 7.0 High · fixed in 2.41.6 : patch util-linux soon.

Data as of 9 Nov 2026, 13:54 UTC

CVSS 3.1 base score
7.0High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (redhat)CVSS 3.17.0
Patch
Available – fixed in 2.41.6
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu 26.10util-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=stonkingOther threatsAffected
  • =2.41.3-3ubuntu2
  • =2.42.2-1ubuntu2
Fixed in–
Ubuntu 26.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=resoluteOther threatsAffected
  • 2.41-4ubuntu4 – 2.41.3-3ubuntu2.2
7 affected builds
Fixed in–
Ubuntu Pro 20.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra/focalOther threatsAffected
  • 2.34-0.1ubuntu2 – 2.34-0.1ubuntu9.6+esm1
13 affected builds
Fixed in–
Ubuntu 18.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=bionicOther threatsAffected
  • 2.30.1-0ubuntu4 – 2.31.1-0.4ubuntu3.7
13 affected builds
Fixed in–
Ubuntu Pro 16.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=esm-infra/xenialOther threatsAffected
  • 2.26.2-6ubuntu3 – 2.27.1-6ubuntu3.10+esm2
20 affected builds
Fixed in–
Ubuntu 14.04 LTSutil-linuxpkg:deb/ubuntu/util-linux?arch=source&distro=trustyOther threatsAffected
  • 2.20.1-5.1ubuntu9 – 2.20.1-5.1ubuntu20.9
19 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade util-linux to version 2.41.6, 2.42.3, or later to apply the official fix. If you cannot patch yet, do not allow unprivileged /etc/fstab entries that specify the X-mount.subdir option. This prevents exploitation by restricting unauthorized mount configurations.

Description

A vulnerability in util-linux's X-mount.subdir option affects versions 2.42 through 2.42.2 when used with Linux kernel 6.15 and later. The issue arises because the open_tree() call uses AT_SYMLINK_NOFOLLOW, which does not prevent traversal of intermediate symlinks, allowing a local unprivileged user with an fstab-authorized X-mount.subdir entry to mount a host path at the intended mountpoint. This can lead to unauthorized file system access and modification.

References

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