CVE-2025-68736

What it actually does

Landlock incorrectly collects access rights for files or directories opened via disconnected bind-mount directories by walking the filesystem hierarchy instead of the mount hierarchy, enabling potential widening of access rights (especially FS_REFER) during renames that would otherwise be denied.

Why it matters to the business

Organizations running Landlock-sandboxed workloads on affected kernels risk unintended file-system access grants that bypass security policies, increasing the chance of data exposure or unauthorized changes inside containers; the issue affects common Chainguard Kyverno images and upstream Linux kernels still in wide use more than 300 days after publication.

How an attack unfolds

An attacker with the ability to create bind mounts and perform renames inside a Landlock domain first opens a disconnected directory through the bind mount, then triggers a rename operation that compares access rights collected from the hidden filesystem hierarchy rather than the mount point; because the collected rights may be broader than the policy intends, the rename succeeds when it should be blocked by LANDLOCK_ACCESS_FS_REFER.

How to fix it

Upgrade the Linux kernel to commit cadb28f8b3fd6908e3051e86158c65c3a8e1c907 or later; for Chainguard images update kyverno, kyverno-background-controller, kyverno-cleanup-controller, kyverno-cli, kyverno-init-container and kyverno-reports-controller to 1.11.5-r17 or newer.

How to confirm the fix worked

Verify the running kernel contains commit cadb28f8b3fd6908e3051e86158c65c3a8e1c907; confirm Chainguard package versions are at or above 1.11.5-r17; exercise Landlock policies that exercise bind-mount and rename operations with disconnected directories and ensure no unexpected access is granted.

Typical attack path

1. Obtain write access to a bind-mount source and read access to the mount point inside the Landlock domain
2. Open a file or directory that becomes disconnected after a rename or move on the underlying filesystem
3. Perform a rename that widens the effective access rights relative to the destination
4. Bypass the intended LANDLOCK_ACCESS_FS_REFER check because rights were collected from the wrong hierarchy

How to detect it

Search kernel audit logs and Landlock-related audit events for unexpected successful renames involving bind mounts; examine process trees that create bind mounts followed by renames inside sandboxed contexts; no public exploitation artifacts are known.

What your security team should do

• Patch kernels and Chainguard Kyverno images to the listed fixed versions as soon as possible
• Review existing Landlock policies for any reliance on bind-mount or rename behavior
• Add runtime kernel version checks to container deployment pipelines
• Monitor for future Landlock-related CVEs given the subsystem's ongoing hardening