CVE-2026-53183
HIGH 7.5In 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.
Severe if exploited (CVSS 7.5), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.5%chance of exploitation in 30 days · 39th percentile
Impact if exploited
7.5CVSS 3.1 · HIGH
- ConfidentialityNone
- IntegrityNone
- AvailabilityHigh
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Weakness (CWE)
Not classified.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
Technical & other
- https://git.kernel.org/stable/c/bf364b0f10b27679140699821f88af7f01e2a6e3
- https://git.kernel.org/stable/c/b1fd13074f22105deec45aa02283e322733e0c2d
- https://git.kernel.org/stable/c/aa3861f40ac32706d9e97bfac76984613e278788
- https://git.kernel.org/stable/c/653245266913f03fcf21cbca68eed5c197a33e52
- https://git.kernel.org/stable/c/c297a4e65c50a2b807d9309b22615080faffa8f3
- https://git.kernel.org/stable/c/da23be77e1292cd611e736c3aa17da633d7ddce7