CVE-2026-78409
Fixed in a distro release EPSS <1%CVSS 7.0
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.
Products: Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4
Distro releases
| Release | Package | Fixed in |
|---|---|---|
| Alpine 3.24 | util-linux | 2.42.3-r0 |
| Debian 12 | util-linux | no fix |
| Debian 13 | util-linux | no fix |
| Debian 14 | util-linux | 2.42.3-1 |
| Red Hat hummingbird 1 | libblkid | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libblkid-devel | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libfdisk | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libfdisk-devel | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | liblastlog2 | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | liblastlog2-devel | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libmount | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libmount-devel | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libsmartcols | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libsmartcols-devel | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libuuid | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | libuuid-devel | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | python3-libmount | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | util-linux | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | util-linux-core | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | util-linux-i18n | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | util-linux-script | 0:2.42.2-3.4.hum1 |
| Red Hat hummingbird 1 | uuidd | 0:2.42.2-3.4.hum1 |
| Ubuntu 14.04 LTS | util-linux | no fix |
| Ubuntu 18.04 LTS | util-linux | no fix |
| Ubuntu 22.04 LTS | util-linux | no fix |
| Ubuntu 24.04 LTS | util-linux | no fix |
| Ubuntu 26.04 LTS | util-linux | no fix |
| Ubuntu 26.10 | util-linux | no fix |
| Ubuntu Pro 16.04 LTS | util-linux | no fix |
| Ubuntu Pro 20.04 LTS | util-linux | no fix |
| openSUSE Tumbleweed | util-linux | 2.42.3-1.1 |