Critical Vulnerability in Linux Kernel: CVE-2025-38491
Summary
CVE-2025-38491: In the Linux kernel, the following vulnerability has been resolved: mptcp: make fallback action and fallback decision atomic Syzkaller reported the following splat: WARNING: CPU: 1 PID: 7704 at net/mptcp/protocol.h:1223... 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 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 platforms, including servers, desktops, and embedded systems. The kernel's functionality includes process management, memory management, device drivers, and system calls. This vulnerability affects multiple Debian versions (11, 12, and 13) of the Linux package, highlighting its significance in maintaining system security.
Vulnerability Detail
CVE-2025-38491 is a vulnerability in the Linux kernel related to the MultiPath TCP (MPTCP) implementation. It was reported by Syzkaller, indicating a potential issue with the atomicity of fallback actions and decisions within the MPTCP protocol. This vulnerability can lead to unexpected behavior in network communications, potentially allowing an attacker to exploit the fallback mechanism, resulting in system instability or unauthorized access. The warning messages generated during the incident provide insight into the specific lines of code affected, indicating a need for immediate attention.
How To Fix
No fixed version is published for this vulnerability.
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Workaround
As a temporary workaround, users may consider disabling MultiPath TCP (MPTCP) functionality if it is not essential for their applications. This can be done by modifying the kernel parameters or configuration files, depending on the specific implementation and usage.
Conclusion
CVE-2025-38491 represents a significant vulnerability in the Linux kernel that requires immediate attention from users of affected Debian versions. By updating to the latest patched version and considering workarounds, users can mitigate the risks associated with this vulnerability. Utilizing tools like Vulert can further enhance security by providing real-time monitoring for open-source vulnerabilities.
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FAQ
CVE-2025-38491 is a vulnerability in the Linux kernel's MultiPath TCP implementation that can lead to system instability and potential unauthorized access.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected by this vulnerability.
The risks include potential system instability, unauthorized access, and exploitation of network communications, which can compromise system security.
Yes, a patched version of the Linux kernel is available. Users should update their packages to the latest version to mitigate the vulnerability.
If immediate updates are not possible, consider disabling MPTCP functionality as a temporary workaround until a proper update can be applied.
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