CVE-2026-78409: Red Hat Enterprise Linux 10

High severity, CVSS 7.0. EPSS: 0.2% chance of exploitation in the next 30 days.

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.

Affected products

• Red Hat Red Hat Enterprise Linux 10
• Red Hat Red Hat Enterprise Linux 7
• Red Hat Red Hat Enterprise Linux 8
• Red Hat Red Hat Enterprise Linux 9
• Red Hat Red Hat Hardened Images: before 2.42.2-3.4.hum1 (fixed in 2.42.2-3.4.hum1)
• Red Hat Red Hat Openshift Container Platform 4

Published 2026-09-02. Last modified 2026-09-03.