CVE-2026-78409: Improper Link Resolution Before File Access ('Link Following') in Red Hat Red Hat Enterprise Linux 10
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.
CVE-2026-78409: Improper Link Resolution Before File Access ('Link Following') in Red Hat Red Hat Enterprise Linux 10
Description
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 v3.1
Score 7.0high
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- redhat
- Date Reserved
- 2026-08-24T14:40:18.012Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-78409","vendor":"Red Hat"}]
Threat ID: 6a9842dfacd9273b4967bbf2
Added to database: 09/02/2026, 15:38:07 UTC
Last updated: 09/02/2026, 15:38:07 UTC
Views: 1
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