Vulnerability in Red Hat Hardened Images
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 metric
CVSS v3 base score 7.0 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.
Affected products
Weakness classification (CWE)
References
- secalert@redhat.com (x_refsource_REDHAT, vdb-entry)
- secalert@redhat.com (x_refsource_REDHAT, issue-tracking)
- secalert@redhat.com
Frequently asked questions
- What is CVE-2026-78409?
- CVE-2026-78409 is a high-severity vulnerability in Red Hat Hardened Images, classified under Improper Link Resolution Before File Access. CVSS score: 7.0/10. Published 2026-09-02.
- How severe is CVE-2026-78409?
- High severity. CVSS v3 base score is 7.0 out of 10.