CVE-2026-78409

7.0 HIGH 0.2% exploit odds Fix listed Other

What it is

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.

At a glance

Exploitability: Can be exploited locally on the machine with a low-privilege account. High risk of data exposure, data tampering, service disruption.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-09-02 16:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-11-05 00:17 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 7.0 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-09-02 16:17 UTC
Last modified: 2026-11-05 00:17 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-59
Record status: Awaiting Analysis

Attack profile CVSS 3.1 · 7.0

Attack vector: Local
Complexity: High
Privileges needed: Low
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Raw vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-78409.md and follow it. Check whether this project is affected by CVE-2026-78409. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record