Critical Memory Management Vulnerability in Linux Kernel: CVE-2025-21939
Summary
DEBIAN-CVE-2025-21939: In the Linux kernel, the following vulnerability has been resolved: drm/xe/hmm: Don't dereference struct page pointers without notifier lock The pnfs that we obtain from hmm_range_fault() point to pages that we don't hav... Affects linux versions < 6.12.19-1. Fixed in 6.12.19-1. How to fix ↓
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Background
The Linux kernel is the core component of the Linux operating system, responsible for managing hardware resources and providing essential services to applications. It is widely used across various devices, from servers to embedded systems. This vulnerability affects the memory management subsystem, specifically in the Direct Rendering Manager (DRM) and Heterogeneous Memory Management (HMM) components, which handle graphics and memory operations.
Vulnerability Detail
In the Linux kernel, a vulnerability has been identified in the DRM and HMM subsystems where dereferencing struct page pointers occurs without holding the necessary notifier lock. This flaw can lead to improper handling of page references, potentially allowing unauthorized access to memory or causing system instability. The issue arises when the kernel attempts to build scatter-gather (sg) tables without ensuring that the pages being referenced are valid, which can result in marking pages as dirty or accessed incorrectly.
How To Fix
Minimum fixed version
6.12.19-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade linuxTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can avoid using the affected features of the DRM and HMM subsystems until the patch is applied. This may involve disabling certain graphics functionalities or avoiding specific operations that rely on these subsystems.
Conclusion
CVE-2025-21939 is a critical vulnerability in the Linux kernel that poses significant risks to system security and stability. It is essential for users to update their systems to the patched version to mitigate these risks. Utilizing tools like Vulert can help in monitoring and identifying vulnerabilities in open-source software.
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FAQ
CVE-2025-21939 is a vulnerability in the Linux kernel that affects memory management, specifically in the DRM and HMM components, leading to potential unauthorized memory access.
You can use Vulert, which monitors open-source vulnerabilities in your software. Simply upload your manifest file like package-lock.json to check for vulnerabilities without needing to install any software.
The risks include potential unauthorized access to memory, system instability, and possible exploitation by malicious actors to execute arbitrary code.
Yes, a patch is available in the form of the Linux kernel version 6.12.19-1. Updating to this version will resolve the vulnerability.
If immediate updates are not possible, consider disabling features that rely on the affected DRM and HMM subsystems as a temporary workaround.
References
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