Answer in brief
CVE-2026-78409 records a Unknown severity vulnerability in Util-linux: util-linux: x-mount.subdir detached-tree resolution can escape via intermediate symlinks. The current sources do not mark it as known exploited. Affected software not mapped in the current feed; confirm the named product and version against your inventory.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
Affected software not mapped in the current feed; confirm the named product and version against your inventory.
Published upstream
Sep 2, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Sep 2, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Sep 2, 2026
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.
Quoted source text, attributed separately from HOL analysis.