Critical Bug Fix in Linux Kernel: ksmbd Vulnerability Resolved
Summary
CVE-2025-21944: In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix bug on trap in smb2_lock If lock count is greater than 1, flags could be old value. 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 various distributions of Debian. It manages system resources and hardware interactions, providing essential services for software applications. The kernel is crucial for system stability and performance. This specific vulnerability affects the ksmbd module, which is responsible for implementing the SMB (Server Message Block) protocol, allowing file sharing and printing services over a network. The vulnerability can lead to system instability and potential crashes if not addressed.
Vulnerability Detail
In the Linux kernel, a bug was identified in the ksmbd module related to the smb2_lock function. If the lock count exceeds one, the flags may retain an old value, leading to a bug-on trap during error handling in the locks_free_lock routine. This could result in system crashes and instability, affecting the overall performance and reliability of systems utilizing the affected kernel versions.
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 mentioned for this vulnerability. It is recommended to apply the patch as soon as it becomes available for your specific Debian version.
Conclusion
The CVE-2025-21944 vulnerability in the Linux kernel's ksmbd module poses a significant risk of system crashes and instability. Users are encouraged to update their systems to the patched version as soon as it becomes available to mitigate these risks. Regular monitoring for updates and utilizing tools like Vulert can help maintain system security.
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FAQ
CVE-2025-21944 is a vulnerability in the Linux kernel's ksmbd module that can cause system crashes due to improper handling of lock flags.
You can use the Vulert platform to check if your application is affected by this vulnerability. Simply upload your manifest file or use the Vulert playground without signup.
The vulnerability can lead to system instability, crashes, and potential data loss, affecting the performance of applications relying on the Linux kernel.
Yes, a patch is available for Debian 13 in version 6.12.19-1. Users of Debian 11 and 12 should monitor for updates.
The urgency level for Debian 11 and 12 has not yet been assigned, but it is advisable to apply the patch as soon as it is released.
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