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.
Published:Sep 2, 2026
Last Modified:Sep 3, 2026
EPS:Sep 2, 2026
EPSS Score:0.00122
CVSS Score:7
Affected Products
Vendor
Product
Action
Vendor
Linux
Product
Util-linux
Linux
Util-linux
Vendor
Redhat
Product
Enterprise Linux
Redhat
Enterprise Linux
Vendor
Redhat
Product
Hardened Images
Redhat
Hardened Images
Vendor
Redhat
Product
Hummingbird
Redhat
Hummingbird
Vendor
Redhat
Product
Openshift
Redhat
Openshift
Vendor
Redhat
Product
Openshift Container Platform
Redhat
Openshift Container Platform
Exploits
No exploit reference
Common Weakness Enumeration
Common Attack Pattern Enumeration and Classification (CAPEC)
Related CVEs
References
Common Vulnerability Scoring System
Attack Vector
Network
Adjacent
Local
Physical
Privileges Required
None
Low
High
User Interaction
None
Required
Scope
Unchanged
Changed
Confidentiality
None
Low
High
Integrity
None
Low
High
Availability
None
Low
High
