Use-After-Free Vulnerability in Linux Kernel's CIFS Client
Summary
CVE-2025-38527: In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-after-free in cifs_oplock_break A race condition can occur in cifs_oplock_break() leading to a use-after-free of the cinode structu... Affects linux versions 5.10.103-1 – 6.9.9-1. No fix is published. How to fix ↓
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Background
The Linux kernel is a core component of the operating system that manages hardware resources and provides essential services for software applications. It supports various file systems, including the Common Internet File System (CIFS), which allows for file sharing over a network. This vulnerability affects the CIFS client, specifically in the handling of oplock breaks, which are mechanisms to optimize file access in networked environments.
Vulnerability Detail
In the Linux kernel, a race condition can occur in the cifs_oplock_break() function, leading to a use-after-free condition of the cinode structure when unmounting a file system. This happens because the function continues to access the cinode after the superblock has been released, resulting in potential memory corruption and system instability. The vulnerability is critical as it can be exploited to execute arbitrary code or crash the system.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, users can avoid unmounting CIFS shares while they are in use, which may help mitigate the risk of exploitation until the package is updated.
Conclusion
The use-after-free vulnerability in the Linux kernel's CIFS client poses serious risks, including potential system crashes and arbitrary code execution. Users are strongly advised to update their systems to the patched versions as soon as possible and to consider temporary workarounds until they can apply the updates.
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FAQ
A use-after-free vulnerability occurs when a program continues to use a memory location after it has been freed, potentially leading to memory corruption and exploitation.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software. Check your application against this vulnerability using the Vulert playground at Vulert Scanner.
Exploitation of this vulnerability can lead to arbitrary code execution, system crashes, or data corruption, posing significant security risks.
Yes, patched versions of the Linux package are available for Debian 12 and 13. Users should update to these versions to mitigate the vulnerability.
If immediate updates are not possible, avoid unmounting CIFS shares while they are in use to reduce the risk of exploitation.
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