mptcp: Clear 'kern' Flag from Fallback Sockets in Linux Kernel

Kernel Updated 02 Oct 2025

Summary

27/12/2021

Disclosed on

N/A

Severity

No i

Fix available

Unrated

Severity

Not published

CVSS Score

GSD-2021-1002746: mptcp: clear 'kern' flag from fallback sockets. Affects Kernel versions >= cf7da0d66cc1a2a19fc5930bb746ffbb2d4cd1be, < c26ac0ea3a91c210cf90452e625dc441adf3e549. No fix is published. How to fix ↓

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Background

The Linux Kernel is the core component of the Linux operating system. It provides essential functionality, such as managing system resources, device drivers, and process scheduling. The MultiPath TCP (MPTCP) is an extension to the TCP protocol that enables the simultaneous use of multiple network paths for a single TCP connection. This allows for improved performance, reliability, and resilience in network communication. However, a vulnerability has been discovered in the MPTCP implementation in the Linux Kernel.

Vulnerability Detail

The vulnerability in the MPTCP implementation allows the 'kern' flag to remain set on fallback sockets. This flag indicates that the socket is a kernel socket and should not be accessible to user-space processes. By not clearing this flag on fallback sockets, an attacker with user-level privileges may be able to access and manipulate these sockets, potentially leading to unauthorized actions or information disclosure. The impact and attack plausibility of this vulnerability have not been proven yet.

How To Fix

No fixed version is published for this vulnerability.

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Workaround

There is no specific workaround mentioned for this vulnerability.

Conclusion

The vulnerability in the MPTCP implementation in the Linux Kernel, which allows the 'kern' flag to remain set on fallback sockets, has been addressed in Linux Kernel version v5.15.11. It is crucial to update the Linux Kernel to the latest version to mitigate the risk of exploitation. For further support on vulnerability remediation, please contact DevNack.com.

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