CVE-2026-78409

ADVISORY - nist

Summary

The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW. That flag does not stop intermediate symlink traversal or keep resolution inside the newly mounted filesystem. A local unprivileged user with an fstab-authorized X-mount.subdir entry can attach a host path at the intended mountpoint.

Common Weakness Enumeration (CWE)

ADVISORY - nist

CWE-59⁠

Improper Link Resolution Before File Access ('Link Following')

Impacted images

Advisories

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