util-linux: TOCTOU Race Condition in util-linux mount(8) - Loop Device Setup (CVE-2026-27456)
Published Last modified Sources: SUSE, Debian, Red Hat, Ubuntu, Msrc Update Guide, CVE.org
What is affected, what to do
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.
Update Util-linux to version 2.41.4.
- Affected
- Util-linux
lt *..2.41.4
- Util-linux
- Fixed in
- Util-linux
2.41.4
- Util-linux
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Metrics
4.7
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
4.7
CVSS v3
Severity Medium on the scale from 0 to 10.
Source: SUSE, Debian, Red Hat, Ubuntu, Msrc Update Guide, CVE.org
0.2 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 4.8
Show all metrics
- Severity
- Medium
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 39.43 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 4.7 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 4.7
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.2 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 4.8
- Low — this CVE sits in the lower 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
- CISA assessment (SSVC)
- Exploitation: proof of concept · not automatable · Technical impact: partial
- Source: CISA Vulnrichment, as of 6 April 2026
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-59, CWE-269, CWE-367
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
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.
Source: suse_csaf, Debian Security Advisories, redhat_csaf, Ubuntu Security Notices, Microsoft Security Update Guide, cvelistv5, NVD (NIST), CVE.org (MITRE)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| util-linux | util-linux |
|
|
| kernel | util-linux |
|
|
Vendors and products
Affected operating systems
| Linux | debian | util-linux | trixie |
| Linux | ubuntu | util-linux | jammy |
| Linux | ubuntu | util-linux | noble |
| Linux | ubuntu | util-linux | resolute |
Weakness classes (CWE)
CWE-59Improper Link Resolution Before File Access ('Link Following')
Base
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
Entry at MITRE CWE-59CWE-269Improper Privilege Management
Class
The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.
Entry at MITRE CWE-269CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
Base
The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
Entry at MITRE CWE-367
References & sources
- github.comutil-linux/util-linux/security/advisories/GHSA-qq4x-vfq4-9h9gx_refsource_CONFIRM
- github.comutil-linux/util-linux/commit/5e390467b26a3cf3fecc04e1a0d482dff3…x_refsource_MISC
- github.comutil-linux/util-linux/releases/tag/v2.41.4x_refsource_MISC
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
One NVD translation into another language is hidden.
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-27456"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-27456.svg?lang=en" alt="CVE-2026-27456 – NEOSEC Intel" height="20"></a>