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CVE-2026-63867

8.2 · HIGH

In the Linux kernel, the following vulnerability has been resolved: mptcp: close TOCTOU race while computing rcv_wnd The MPTCP output path access locklessly the MPTCP-level ack_seq in multiple ti…

Published Jul 19, 2026EPSS 0.34%

Overview

CVE-2026-63867 is a high-severity vulnerability. It was published on July 19, 2026 and has a CVSS 3.1 base score of 8.2 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.2, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

mptcp: close TOCTOU race while computing rcv_wnd

The MPTCP output path access locklessly the MPTCP-level ack_seq

in multiple times, using possibly different values for the data_ack

in the DSS option and to compute the announced rcv wnd for the same

packet.

Refactor the cote to avoid inconsistencies which may confuse the

peer. Also ensure that the MPTCP level rcv wnd is updated only when

the egress packet actually contains a DSS ack.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/301a33fd590c408a05c5df800e0cc1e6a8a2f8f8Refgit.kernel.org/stable/c/3b8cbba7c0ed31189c89f90be247b8973ffa79efRefgit.kernel.org/stable/c/68364963e5baf03f16b4420292291f75c8f66497Refgit.kernel.org/stable/c/8ab24fdebc369c0dfb90f82c1650b1e66662bb45Refgit.kernel.org/stable/c/8f4f0a157e8436a05bf8c3670b24dbc258911c43Refgit.kernel.org/stable/c/907ac6b1658e0277f979fcdfae2a753b495c1510Refgit.kernel.org/stable/c/c4f4cf60797974873dbc8e100144682a6f2f861f

How CyberStrike helps

Frequently asked questions

What is CVE-2026-63867?

CVE-2026-63867 is a high-severity vulnerability. It was published on July 19, 2026 and has a CVSS 3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-63867?

This vulnerability has a CVSS 3.1 base score of 8.2, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-63867?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-63867?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-63867 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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