CVE-2026-78409

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.

CVSS v3 7.0 HIGH

7.0^/10

CVSS v3 : HIGH

Vector :

Exploitability : 1.0 / Impact : 5.9

Attack Vector LOCAL

Attack Complexity HIGH

Privileges Required LOW

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://access.redhat.com/errata/RHSA-2026:63162
https://access.redhat.com/security/cve/CVE-2026-78409
https://bugzilla.redhat.com/show_bug.cgi?id=2522607
https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv
https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv

Configurations

No configuration.

History

No history.

Information

Published : 2026-09-02 16:17

Updated : 2026-09-03 18:12

NVD link : CVE-2026-78409

Mitre link : CVE-2026-78409

CVE.ORG link : CVE-2026-78409

JSON object : View

Products Affected

No product.

CWE

CWE-59

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

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