CVE-2026-53183: mptcp: allow subflow rcv wnd to shrink
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 rcvnxt 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.
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-53183?
The severity of CVE-2026-53183 is high with a score of 7.5.
What type of vulnerability is CVE-2026-53183?
CVE-2026-53183 is a vulnerability in the Linux kernel related to the MultiPath TCP (MPTCP) implementation.
How does CVE-2026-53183 affect systems?
CVE-2026-53183 allows the receive window to shrink in MPTCP connections, which can potentially impact data transmission.
How can I mitigate CVE-2026-53183?
To mitigate CVE-2026-53183, update to the latest version of the Linux kernel where this vulnerability is resolved.
Is CVE-2026-53183 exploitable remotely?
Yes, CVE-2026-53183 is marked with AV:N, indicating it can be exploited over the network.