Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
CVE-2026-78409
Red Hat Red Hat Hardened Images — Util-linux: util-linux: x-mount.subdir detached-tree resolution can escape via intermediate symlinks
AV AC PR UI S C I A CVSS EPSS %ile KEV
L H L N U H H H 7.0 .0015 3.9 —
AFFECTED
Product Versions Fixed
Red Hat Hardened Images unspecified 2.42.2-3.4.hum1
Red Hat Enterprise Linux 10 unspecified —
Red Hat Enterprise Linux 7 unspecified —
Red Hat Enterprise Linux 8 unspecified —
Red Hat Enterprise Linux 9 unspecified —
Red Hat Enterprise Linux 9 unspecified —
Red Hat Enterprise Linux 9 unspecified —
Red Hat OpenShift Container Platform 4 unspecified —
TIMELINE
Aug 24 Reserved by redhat
Sep 2 Published (CNA: redhat)
Sep 3 PATCH SHIPPED — CVE-2026-78409 (Red Hat Hardened Images). Fixed in Red Hat Hardened Images 2.42.2-3.4.hum1.
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.
Lifecycle
Complete event history — 3 events, chronological
| Date | Event | Detail |
|---|
| August 24, 2026 | Reserved | Reserved by redhat |
| September 2, 2026 | Published | Published (CNA: redhat) |
| September 3, 2026 | PATCH SHIPPED | PATCH SHIPPED — CVE-2026-78409 (Red Hat Hardened Images). Fixed in Red Hat Hardened Images 2.42.2-3.4.hum1. |
Affected
Affected products and packages — 8 rows
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|
| Red Hat | Red Hat Hardened Images | — | — | 2.42.2-3.4.hum1 |
| 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 Enterprise Linux 9 | — | — | — |
| Red Hat | Red Hat Enterprise Linux 9 | — | — | — |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — | — |
About this page
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-78409 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.
