CVE-2026-53183
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.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.48%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.48% probability · 40th percentile
- CISA KEV
- Not listed
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
References
- https://git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52Patch
- https://git.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788Patch
- https://git.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2dPatch
- https://git.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3Patch
- https://git.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3Patch
- https://git.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7Patch
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.