A flaw in util‑linux’s libmount component causes the library to proceed with post‑mount hooks even when an external mount helper has failed. This omission allows an unprivileged user to run privileged operations through the X‑mount.idmap or X‑mount.owner hooks, effectively giving them the ability to clone filesystems that retain set‑uid bits or to modify permissions on existing inodes. The weakness corresponds to missing error handling (CWE‑390).

The vulnerability affects versions of util‑linux up to 2.41.5 and 2.42.2 on Linux distributions that incorporate the util‑linux package. All systems using these releases run the libmount library and are therefore potentially exposed.

The CVSS score of 8.5 marks the issue as high severity, and although an EPSS score is not listed, the lack of a KEV listing does not diminish the risk. Attackers are likely able to exploit this flaw locally by invoking the mount command with a helper that fails, then leveraging the privileged post‑mount hooks to gain elevated privileges. If a system allows untrusted users to mount filesystems or to specify custom X‑mount hooks, the privilege escalation can be achieved with minimal effort.