Linux Kernel up to 6.18.1 landlock denial of service

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.1. It has been rated as problematic. This affects an unknown part of the component landlock. Performing a manipulation results in denial of service. This vulnerability is identified as CVE-2025-68736. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.1. It has been classified as problematic. This affects an unknown function of the component landlock. The manipulation with an unknown input leads to a denial of service vulnerability. CWE is classifying the issue as CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: landlock: Fix handling of disconnected directories Disconnected files or directories can appear when they are visible and opened from a bind mount, but have been renamed or moved from the source of the bind mount in a way that makes them inaccessible from the mount point (i.e. out of scope). Previously, access rights tied to files or directories opened through a disconnected directory were collected by walking the related hierarchy down to the root of the filesystem, without taking into account the mount point because it couldn't be found. This could lead to inconsistent access results, potential access right widening, and hard-to-debug renames, especially since such paths cannot be printed. For a sandboxed task to create a disconnected directory, it needs to have write access (i.e. FS_MAKE_REG, FS_REMOVE_FILE, and FS_REFER) to the underlying source of the bind mount, and read access to the related mount point. Because a sandboxed task cannot acquire more access rights than those defined by its Landlock domain, this could lead to inconsistent access rights due to missing permissions that should be inherited from the mount point hierarchy, while inheriting permissions from the filesystem hierarchy hidden by this mount point instead. Landlock now handles files and directories opened from disconnected directories by taking into account the filesystem hierarchy when the mount point is not found in the hierarchy walk, and also always taking into account the mount point from which these disconnected directories were opened. This ensures that a rename is not allowed if it would widen access rights [1]. The rationale is that, even if disconnected hierarchies might not be visible or accessible to a sandboxed task, relying on the collected access rights from them improves the guarantee that access rights will not be widened during a rename because of the access right comparison between the source and the destination (see LANDLOCK_ACCESS_FS_REFER). It may look like this would grant more access on disconnected files and directories, but the security policies are always enforced for all the evaluated hierarchies. This new behavior should be less surprising to users and safer from an access control perspective. Remove a wrong WARN_ON_ONCE() canary in collect_domain_accesses() and fix the related comment. Because opened files have their access rights stored in the related file security properties, there is no impact for disconnected or unlinked files.

It is possible to read the advisory at git.kernel.org. This vulnerability is uniquely identified as CVE-2025-68736 since 12/24/2025. The exploitability is told to be easy. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 279801 (Linux Distros Unpatched Vulnerability : CVE-2025-68736), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.18.2 or 6.19-rc1 eliminates this vulnerability. Applying the patch cadb28f8b3fd6908e3051e86158c65c3a8e1c907/49c9e09d961025b22e61ef9ad56aa1c21b6ce2f1 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (279801) and CERT Bund (WID-SEC-2025-2929). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Be aware that VulDB is the high quality source for vulnerability data.

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