CVE-2026-76642
CVE-2026-76642 is a high-severity vulnerability with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-390.
Key facts
- Severity: High (CVSS 3.x base score 7.8)
- CVSS v4: 8.5
- EPSS exploit prediction: 0% (11th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-390
- Published:
- Last modified:
Description
util-linux versions through 2.41.5 and 2.42.2 fail to check mount helper exit status before running post-mount hooks, allowing unprivileged users to execute privileged operations on pre-existing filesystems. Attackers can exploit X-mount.idmap or X-mount.owner hooks to clone filesystems with inherited suid bits or modify target inode permissions after a helper fails, achieving privilege escalation.
Frequently asked questions
- What is CVE-2026-76642?
- util-linux versions through 2.41.5 and 2.42.2 fail to check mount helper exit status before running post-mount hooks, allowing unprivileged users to execute privileged operations on pre-existing filesystems. Attackers can exploit X-mount.idmap or X-mount.owner hooks to clone filesystems with inherited suid bits or modify target inode permissions after a helper fails, achieving privilege escalation.
- How severe is CVE-2026-76642?
- CVE-2026-76642 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
- Is CVE-2026-76642 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-76642?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2026-76642 published?
- CVE-2026-76642 was published on 2026-09-03 and last updated on 2026-09-24.
References
- https://github.com/util-linux/util-linux
- https://github.com/util-linux/util-linux/blob/v2.42.2/libmount/src/context_mount.c#L476
- https://github.com/util-linux/util-linux/blob/v2.42.2/libmount/src/context_mount.c#L892
- https://github.com/util-linux/util-linux/commit/1d14676ea70003e9f5b2a6a76af0cadb1190411a
- https://github.com/util-linux/util-linux/commit/a15c00a9e545aa8b9cf6ec0f888ff6c7b3eaeedc
- https://github.com/util-linux/util-linux/commit/f57cea130839c0af8dc0525274267ae4cfd66bbf
- https://github.com/util-linux/util-linux/security/advisories/GHSA-m25x-3hj9-m26f
- https://www.vulncheck.com/advisories/util-linux-libmount-privilege-escalation-via-failed-mount-helper
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