Riskcovery

CVE-2026-53183

mptcp: allow subflow rcv wnd to shrink

State
Published
Severity
7.5 High
Published
Jun 25, 2026
Updated
Oct 19, 2026
Reserved
Jun 9, 2026

Read the record on cve.org

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.

Scores

CVSSScoreVectorSource
3.17.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HLinux

Weaknesses

  • CWE-400 Uncontrolled Resource Consumption

Affected Products

ProductVersions
LinuxLinux
  • f3589be0c420a3137e5902d15705ced6a36f3f43 to before bf364b0f10b27679140699821f88af7f01e2a6e3Affected
  • f3589be0c420a3137e5902d15705ced6a36f3f43 to before b1fd13074f22105deec45aa02283e322733e0c2dAffected
  • f3589be0c420a3137e5902d15705ced6a36f3f43 to before aa3861f40ac32706d9e97bfac76984613e278788Affected
  • f3589be0c420a3137e5902d15705ced6a36f3f43 to before 653245266913f03fcf21cbca68eed5c197a33e52Affected
  • f3589be0c420a3137e5902d15705ced6a36f3f43 to before c297a4e65c50a2b807d9309b22615080faffa8f3Affected
  • f3589be0c420a3137e5902d15705ced6a36f3f43 to before da23be77e1292cd611e736c3aa17da633d7ddce7Affected
LinuxLinux
  • 5.19Affected
  • before 5.19Not affected
  • 6.1.176 through 6.1.*Not affected
  • 6.6.143 through 6.6.*Not affected
  • 6.12.94 through 6.12.*Not affected
  • 6.18.36 through 6.18.*Not affected
  • 7.0.13 through 7.0.*Not affected
  • 7.1 and laterNot affected

References

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