Linux Kernel Lockdown Check debugfs mmap_prepare privileges management

Summaryinfo

A vulnerability was found in Linux Kernel. It has been rated as very critical. Affected is the function mmap_prepare of the file debugfs of the component Lockdown Check. This manipulation causes privileges management. This vulnerability is tracked as CVE-2026-89745. The attack is possible to be carried out remotely. No exploit exists. It is suggested to install a patch to address this issue.

Detailsinfo

A vulnerability was found in Linux Kernel (version unknown). It has been declared as very critical. Affected by this vulnerability is the function mmap_prepare of the file debugfs of the component Lockdown Check. The manipulation 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. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: debugfs: Fix lockdown check for mmap_prepare Commit 651fdda8406d ("relay: update relay to use mmap_prepare") changed the `mmap` file operation to `mmap_prepare` for relayfs, but the lockdown check in debugfs was not updated accordingly. This prevents debugfs from being locked down when the kernel is in integrity mode if a file uses `mmap_prepare` but not `mmap`. Since the conversion to `mmap_prepare` across the kernel is not yet complete, update the lockdown check to look for both `mmap` and `mmap_prepare` to ensure comprehensive coverage.

The advisory is shared at git.kernel.org. This vulnerability is known as CVE-2026-89745 since 09/11/2026. The exploitation appears to be easy. The attack can be launched remotely. Additional levels of successful authentication are required for exploitation. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 09/11/2026). MITRE ATT&CK project uses the attack technique T1068 for this issue.

Applying the patch 651fdda8406d/e7f6a6b5741d16fdac7adaecbe0fa52ae756f208 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

License

• open-source

Website

• Vendor: https://www.kernel.org/

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