Red Hat Enterprise Linux X-mount open_tree subdir privileges management

Summaryinfo

A vulnerability classified as very critical was found in Red Hat Enterprise Linux, Hardened Images and OpenShift Container Platform. Affected is the function open_tree of the component X-mount. Executing a manipulation of the argument subdir can lead to privileges management. This vulnerability appears as CVE-2026-78409. The attack requires local access. There is no available exploit.

Detailsinfo

A vulnerability classified as very critical was found in Red Hat Enterprise Linux, Hardened Images and OpenShift Container Platform (version unknown). This vulnerability affects the function open_tree of the component X-mount. The manipulation of the argument subdir with an unknown input leads to a privileges management vulnerability. The CWE definition for the vulnerability is CWE-269. The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at access.redhat.com. This vulnerability was named CVE-2026-78409 since 08/24/2026. The exploitation appears to be easy. The attack needs to be approached locally. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 09/02/2026). The MITRE ATT&CK project declares the attack technique as T1068.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-70107). Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Red Hat

Name

• Enterprise Linux
• Hardened Images
• OpenShift Container Platform

License

• commercial

Website

• Vendor: https://www.redhat.com/

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Once again VulDB remains the best source for vulnerability data.

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