Host-path exposure via intermediate symlink traversal
Published Sep 2, 2026 · Updated Sep 3, 2026
Link following in util-linux mount allows local users to expose host paths through a restricted fstab-authorized mountpoint. The detached-tree X-mount.subdir path passes an untrusted subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW, which still follows intermediate symlinks and permits resolution outside the new filesystem. Exploitation requires Linux 6.15 or later, SUID mount, an authorized user fstab entry, and attacker-controlled filesystem content; exposed paths can be read or modified when additional mount hooks permit it.
Summary
What happened
Link following in util-linux mount allows local users to expose host paths through a restricted fstab-authorized mountpoint. The detached-tree X-mount.subdir path passes an untrusted subdirectory to open_tree() with AT_SYMLINK_NOFOLLOW, which still follows intermediate symlinks and permits resolution outside the new filesystem. Exploitation requires Linux 6.15 or later, SUID mount, an authorized user fstab entry, and attacker-controlled filesystem content; exposed paths can be read or modified when additional mount hooks permit it.
The record
- CVE
- CVE-2026-78409
- Published
- Sep 2, 2026
- Updated
- Sep 3, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Hardened Images
- Classifications
- CWE-59, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Sep 2, 2026CVE publishedPublication date reported by the CVE source.
- Sep 3, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Detached-tree X-mount.subdir escape proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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