CVE-2026-53183
mptcp: allow subflow rcv wnd to shrink
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.
INFO
Published Date :
June 25, 2026, 8:38 a.m.
Last Modified :
June 25, 2026, 8:38 a.m.
Remotely Exploit :
No
Source :
Linux
Affected Products
The following products are affected by CVE-2026-53183
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Update the Linux kernel to include the MPTCP fix.
- Ensure netns settings do not prevent subflow window shrinking.
- Monitor receiver buffer usage after the update.
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