Critical Vulnerability in Linux Kernel: MPTCP Suboption Status Consolidation Issue
Summary
CVE-2025-21707: In the Linux kernel, the following vulnerability has been resolved: mptcp: consolidate suboption status MPTCP maintains the received sub-options status is the bitmask carrying the received suboptions and in several bitfi... Affects linux versions < 6.1.129-1. Fixed in 6.1.129-1. How to fix ↓
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Background
The Linux kernel is the core component of many operating systems, providing essential services for all other parts of the system. It manages hardware resources, system calls, and processes. The kernel supports various networking protocols, including MultiPath TCP (MPTCP), which enhances TCP by allowing multiple paths for data transmission. This vulnerability affects the MPTCP implementation, specifically in how it handles suboption statuses, potentially leading to inconsistent states and uninitialized values.
Vulnerability Detail
The vulnerability, identified as CVE-2025-21707, arises from the MPTCP's handling of received sub-options. The code fails to adequately clear certain bitfields after parsing suboptions, leading to uninitialized values being used in subsequent operations. This flaw can be exploited to trigger undefined behavior in the kernel, potentially leading to system crashes or security breaches. The issue was discovered by syzbot, which highlighted the fragility of the current implementation and the risks associated with uninitialized memory.
How To Fix
Minimum fixed version
6.1.129-1
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.
Conclusion
The CVE-2025-21707 vulnerability in the Linux kernel's MPTCP implementation poses significant risks due to improper handling of suboption statuses. Users are advised to update their systems promptly to mitigate potential impacts. Utilizing tools like Vulert can help in monitoring vulnerabilities effectively.
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FAQ
CVE-2025-21707 is a vulnerability in the Linux kernel's MPTCP implementation that can lead to uninitialized memory usage and potential system instability.
Exploitation of this vulnerability can lead to crashes or security breaches, affecting the stability and security of systems running the vulnerable kernel.
If you are using Debian 12 or 13 with the Linux kernel, your system may be affected. Check for updates to ensure you are running a patched version.
You can use Vulert, which monitors open-source vulnerabilities in real-time. Visit Vulert Scanner to check if your application is affected without needing to sign up.
While there are no specific workarounds, it is crucial to monitor for updates and apply them as soon as they are available to mitigate risks.
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