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CVE-2026-53183

7.5 · HIGH

In the Linux kernel, the following vulnerability has been resolved: mptcp: allow subflow rcv wnd to shrink In MPTCP connection, the `window` field in the TCP header refers to the MPTCP-level rcv_…

Published Jun 25, 2026EPSS 0.49%

Overview

CVE-2026-53183 is a high-severity vulnerability. It was published on June 25, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, 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: allow subflow rcv wnd to shrink

In MPTCP connection, the `window` field in the TCP header refers to the

MPTCP-level rcv_nxt and it's right edge should not move backward. Such

constraint is enforced at DSS option generation time.

At the same time, the TCP stack ensures independently that the TCP-level

rcv wnd right's edge does not move backward. That in turn causes artificial

inflating of the MPTCP rcv window when the incoming data is acked at the

TCP level and is OoO in the MPTCP sequence space (or lands in the backlog).

As a consequence, the incoming traffic can exceed the receiver rcvbuf size

even when the sender is not misbehaving.

Prevent such scenario forcibly allowing the TCP subflow to shrink the

TCP-level rcv wnd regardless of the current netns setting.

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/653245266913f03fcf21cbca68eed5c197a33e52Refgit.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788Refgit.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2dRefgit.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3Refgit.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3Refgit.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7

How CyberStrike helps

Frequently asked questions

What is CVE-2026-53183?

CVE-2026-53183 is a high-severity vulnerability. It was published on June 25, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-53183?

This vulnerability has a CVSS 3.1 base score of 7.5, 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-2026-53183?

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-2026-53183?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-53183 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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