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.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Red Hat | Red Hat Hardened Images | — | — |
| 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 OpenShift Container Platform 4 | — | — |
| Red Hat | Red Hat OpenShift Container Platform 5 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | util-linux | 2.42.3-1 | — |
| Debian 13 | util-linux | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | util-linux | No fix yet | — |
| Ubuntu 26.04 LTS | util-linux | No fix yet | — |
| Ubuntu 18.04 LTS | util-linux | No fix yet | — |
| Ubuntu 14.04 LTS | util-linux | No fix yet | — |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | util-linux | No fix yet | — |
| Ubuntu Pro 16.04 LTS | util-linux | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Red Hat Hardened Images 1 | uuidd +17 | 2.42.2-3.4.hum1 | RHSA-2026:63162 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | util-linux | 2.42.3-1.1 | openSUSE-SU-2026:11870-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | util-linux | 2.42.3-r0 | — |
Advisories 3
- WID-SEC-2026-3160 util-linux: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 4, 2026
- RHSA-2026:63162 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- openSUSE-SU-2026:11870-1 libblkid-devel-2.42.3-1.1 on GA media SUSE / openSUSE Security Updates · Sep 24, 2026
References
- RHSA-2026:63162 vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-78409 vdb-entry
- RHBZ#2522607 issue-tracking
- https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv