Integer Overflow Vulnerability in Linux Kernel's CIFS Package
Summary
CVE-2025-21962: In the Linux kernel, the following vulnerability has been resolved: cifs: Fix integer overflow while processing closetimeo mount option User-provided mount parameter closetimeo of type u32 is intended to have an upper li... Affects linux versions < 6.1.133-1. Fixed in 6.1.133-1. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, including Debian. It manages system resources and hardware communication. The CIFS (Common Internet File System) module allows for file sharing over a network. This vulnerability affects the way user-provided mount parameters are processed, specifically the 'closetimeo' option, which can lead to severe system instability if exploited.
Vulnerability Detail
In the Linux kernel, an integer overflow occurs when processing the user-provided mount parameter 'closetimeo' of type u32. This parameter is intended to have an upper limit, but it is converted from seconds to jiffies without proper validation. This oversight can lead to an overflow, potentially causing unexpected behavior or system crashes. The vulnerability was discovered by the Linux Verification Center and is critical for maintaining system integrity.
How To Fix
Minimum fixed version
6.1.133-1
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
Currently, there are no specific workarounds provided for this vulnerability. It is recommended to apply the patch as soon as it becomes available to mitigate risks.
Conclusion
The integer overflow vulnerability in the Linux kernel's CIFS package poses a significant risk to system stability. It is crucial to update to the patched version as soon as it is available to ensure the integrity of your system. Regular monitoring and vulnerability management practices, such as using tools like Vulert, can help maintain security.
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FAQ
The 'closetimeo' mount option specifies the timeout for closing a CIFS connection, measured in seconds.
Exploiting this vulnerability could lead to system crashes or instability, affecting the reliability of file sharing operations.
If you are running a version of the Linux kernel prior to the patched version (6.12.20-1 for Debian 13), your system may be vulnerable.
You can check your current Linux kernel version by running the command 'uname -r' in your terminal.
Vulert monitors open-source vulnerabilities in software using a manifest file like package-lock.json. You can check if your application is affected by this vulnerability using the Vulert playground without any signup.
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