Integer Overflow Vulnerability in Linux Kernel's CIFS Package
Summary
CVE-2025-21963: In the Linux kernel, the following vulnerability has been resolved: cifs: Fix integer overflow while processing acdirmax mount option User-provided mount parameter acdirmax of type u32 is intended to have an upper limit,... Affects linux versions < 6.1.133-1. Fixed in 6.1.133-1. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
The Linux kernel is a core component of many operating systems, providing essential services for hardware and software interaction. It supports a wide range of functionalities, including file systems, process management, and network protocols. The CIFS (Common Internet File System) is a network file sharing protocol that allows applications to read and write to files and request services from server programs. This vulnerability specifically affects the CIFS implementation in Debian versions 12 and 13, highlighting a critical flaw in how user-provided mount parameters are processed.
Vulnerability Detail
In the Linux kernel, an integer overflow vulnerability has been identified in the CIFS module. The issue arises when the user-provided mount parameter 'acdirmax' of type u32 is converted from seconds to jiffies without proper validation. This conversion can lead to an integer overflow, potentially allowing an attacker to manipulate the mount option and cause unexpected behavior in the system. This vulnerability was discovered by the Linux Verification Center and poses risks such as system instability or unauthorized access to resources.
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. Users are advised to apply the patch as soon as it becomes available to mitigate the risks associated with this integer overflow issue.
Conclusion
The integer overflow vulnerability in the CIFS module of the Linux kernel poses significant risks to systems running affected versions. Users are encouraged to update their packages to the patched version to ensure system stability and security. Monitoring tools like Vulert can assist in identifying vulnerabilities in real-time.
See every vulnerability recorded for linux →
FAQ
The vulnerability is an integer overflow in the CIFS module of the Linux kernel, which can lead to system instability.
The vulnerability affects Debian versions 12 and 13 of the Linux kernel.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities in your software. Check your application against the vulnerability using the Vulert playground.
Yes, a patch is available for Debian 13 in version 6.12.20-1. Users of Debian 12 should monitor for updates.
While there are no specific workarounds, it is crucial to apply the patch as soon as possible to mitigate risks.
Related vulnerabilities
Recent vulnerabilities recorded for linux.
