CVE-2026-78409Util-linux: util-linux: x-mount.subdir detached-tree resolution can escape via intermediate symlinks
Updated under an hour ago ()
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It affects Red Hat Hardened Images and 2 other products. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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
- 7.0 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
- Weakness (CWE)
- CWE-59
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- redhat
- NVD analysis
- Awaiting Analysis
- Record last updated
- Sep 3, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
Red Hat Red Hat Hardened Images redhat:hummingbird | from 2.42.2-3.4.hum1 not affected | CNA record |
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux | 10 | CNA record |
Red Hat Red Hat OpenShift Container Platform 4 redhat:openshift | 4 | CNA record |
References
- https://access.redhat.com/errata/RHSA-2026:63162vendor-advisory, x-refsource-redhat
- https://access.redhat.com/security/cve/CVE-2026-78409vdb-entry, x-refsource-redhat
- https://bugzilla.redhat.com/show_bug.cgi?id=2522607issue-tracking, x-refsource-redhat
- https://github.com/util-linux/util-linux/security/advisories/GHSA-8f2p-47x3-43mv
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.