The X-mount.subdir option uses a detached-tree fast path on Linux 6.15 and later and passes the configured subdirectory…
Summary
Vulnerability reported (CVE-2026-78409). Successful exploitation can lead to full system takeover.
AI summary
Produced by SecPulse using an external AI model; it may contain mistakes. Check the original description and references below before acting on it.
A vulnerability tracked as CVE-2026-78409 has been found.
Successful exploitation can lead to full system takeover. CVSS score: 7.0/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "CVE-2026-78409" on the vendor's site.
CVE-2026-78409 — CWE-59 / CVSS v3 7.0
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-59) has been reported.
Check the vendor advisory for the affected versions.
Severity: High (CVSS 7.0/10). Successful exploitation can lead to full system takeover.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1
Identify exposureidentify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで影響コンポーネントを特定する。
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2
Post-deployment verificationverify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Records published by each distribution for this CVE. Fixed versions differ by release; check each link.
- Alpine Linux ALPINE-CVE-2026-78409 util-linux Fix available
- Debian DEBIAN-CVE-2026-78409 util-linux Fix available
- Ubuntu UBUNTU-CVE-2026-78409 util-linux No fixed version in this record
Original description The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD
References
- web secalert@redhat.com
- web secalert@redhat.com
- web secalert@redhat.com
- web github.com