Read the docs
TI-2026-21863 Aliases CVE-2026-27456

util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup

Priority MEDIUM 55CWE-269Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
High
Impact type
Privilege escalation, Information disclosure
Confidentiality · integrity · availability
High · None · None
Fix status
Partial Red Hat: 5 fixed, 4 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-269, CWE-59 and the CVSS impact.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00157 4th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial util-linux (util-linux): 2.41.4Red Hat: 3 advisoriesRed Hat: 5 fixed, 4 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
util-linuxutil-linuxbefore 2.41.42.41.4Patch availableCNA
  • util-linux Vendorutil-linux Affected before 2.41.4 Fixed in 2.41.4 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:kernel:util-linux:*:*:*:*:*:*:*:*before 2.41.4Vulnerablekernel
  • cpe:2.3:a:kernel:util-linux:*:*:*:*:*:*:*:* Versions before 2.41.4 Vulnerable ·kernel

Remediation

  • Fix · CNA util-linux (util-linux) Fixed in 2.41.4

Red Hat 3 advisories

  • RHSA-2026:95365 Released 2026-11-04 · Red Hat rating Critical
    Red Hat Cost Management On-Premise container image update
    • Red Hat Cost Management On-Premise 1 registry.redhat.io/costmanagement/costmanagement-ui-rhel10
  • RHSA-2026:93461 Released 2026-11-02 · Red Hat rating Important
    util-linux security update
    • Red Hat Enterprise Linux AppStream (v. 10) libblkid-devel-2.40.2-18.el10_2.20, libmount-devel-2.40.2-18.el10_2.20, libuuid-devel-2.40.2-18.el10_2.20 +2
    • Red Hat Enterprise Linux BaseOS (v. 10) libblkid-2.40.2-18.el10_2.20, libfdisk-2.40.2-18.el10_2.20, libmount-2.40.2-18.el10_2.20 +4
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) libfdisk-devel-2.40.2-18.el10_2.20, libsmartcols-devel-2.40.2-18.el10_2.20
  • RHSA-2026:7180 Released 2026-04-09 · Red Hat rating Moderate
    Red Hat Hardened Images RPMs bug fix and enhancement update
    • Red Hat Hardened Images util-linux-2.42-7.1.hum1@aarch64, util-linux-2.42-7.1.hum1@src, util-linux-2.42-7.1.hum1@x86_64 +6

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 8AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 9AffectedNo fix yet: Fix deferred
Red Hat OpenShift AI (RHOAI)Affected—
Red Hat OpenShift Container Platform 4AffectedNo fix yet: Fix deferred
Red Hat Cost Management On-Premise 1Fixed RHSA-2026:95365
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:93461
Red Hat Enterprise Linux BaseOS (v. 10)Fixed RHSA-2026:93461
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:93461
Red Hat Hardened ImagesFixed RHSA-2026:7180
Not affected: 4 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Hardened Images
  • Red Hat OpenShift AI (RHOAI)

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-27456
  2. 2026-11-02 Fix available: RHSA-2026:93461 · Red Hat
  3. 2026-11-02 Fix available: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) · Red Hat
  4. 2026-11-06 Fix available: Red Hat Cost Management On-Premise 1 · Red Hat
  5. 2026-11-06 Fix available: RHSA-2026:95365 · Red Hat
  6. 2026-11-06 Affected versions changed · Red Hat

References

Exploit 1

Patch 1

Other 1

  • TI-2026-53553 util-linux libmount Privilege Escalation via Failed Mount Helper CVSS 4.0HIGH 8.5
  • TI-2026-73994 Race condition in util-linux mount hook allows privilege escalation CVSS 3.1HIGH 7.0
  • TI-2026-74163 Integer overflow in util-linux libblkid DOS extended partition parsing CVSS 3.1HIGH 8.0
  • TI-2026-73996 util-linux LIBMOUNT_FORCE_MOUNT2 allows nosuid and noexec bypass CVSS 3.1HIGH 7.0
  • TI-2026-73995 Race condition in util-linux mount lets local users gain root CVSS 3.1HIGH 7.0
  • TI-2025-12886 Util-linux: util-linux: heap buffer overread in setpwnam() when processing 256-byte usernames CVSS 3.1MEDIUM 6.1

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences