Use-After-Free Vulnerability in Linux Kernel - Impacting Debian Packages
Summary
CVE-2025-39881: In the Linux kernel, the following vulnerability has been resolved: kernfs: Fix UAF in polling when open file is released A use-after-free (UAF) vulnerability was identified in the PSI (Pressure Stall Information) monito... Affects linux versions < 6.1.153-1. Fixed in 6.1.153-1. How to fix ↓
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Background
The Linux kernel is the core component of the Linux operating system, responsible for managing system resources and facilitating communication between hardware and software. It is widely used across various distributions, including Debian. This vulnerability affects the kernel's PSI (Pressure Stall Information) monitoring mechanism, which is crucial for managing system performance under load. The vulnerability can lead to instability and potential system crashes if exploited.
Vulnerability Detail
In the Linux kernel, a use-after-free (UAF) vulnerability has been identified in the PSI monitoring mechanism. This issue arises when a file descriptor is released while another process still holds a reference to it, leading to potential access to freed memory. The specific bug occurs in the function psi_trigger_poll, where a read operation attempts to access memory that has already been freed, resulting in undefined behavior and possible system crashes. The vulnerability is particularly concerning as it can be exploited during the polling of cgroup pressure files, which are used to monitor resource usage in containerized environments.
How To Fix
Minimum fixed version
6.1.153-1
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 enabling and disabling cgroup pressure monitoring in quick succession, which can trigger the vulnerability. Instead, ensure that monitoring is only toggled when necessary and allow sufficient time between changes.
Conclusion
The identified use-after-free vulnerability in the Linux kernel poses significant risks to system stability and security. Users are strongly advised to update their systems to the latest patched versions to mitigate these risks. Additionally, utilizing tools like Vulert can enhance your ability to monitor and respond to vulnerabilities in your software.
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FAQ
A use-after-free vulnerability occurs when a program continues to use a pointer after the memory it points to has been freed, potentially leading to crashes or arbitrary code execution.
You can use Vulert, which monitors open-source vulnerabilities in your software. By uploading your manifest file like package-lock.json, you can check for vulnerabilities without needing to install any software.
Exploitation of this vulnerability can lead to system instability, crashes, and potential unauthorized access to system resources, impacting overall system security.
Yes, updating to version 6.1.153-1 for Debian 12, 6.12.48-1 for Debian 13, or any later version for Debian 14 will mitigate this vulnerability.
Using tools like Vulert can help you monitor and receive alerts about open-source vulnerabilities in real-time, ensuring you are always informed about potential risks.
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