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.

A flaw was found in the Linux kernel's Multipath TCP (MPTCP) implementation. This vulnerability occurs because the TCP stack independently manages the TCP-level receive window, which can lead to an artificial inflation of the MPTCP receive window. A remote attacker could exploit this by sending specific traffic, causing the incoming data to exceed the receiver's buffer size. This can result in a Denial of Service (DoS) condition, making the system unresponsive to legitimate traffic.

Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-53183 https://nvd.nist.gov/vuln/detail/CVE-2026-53183 https://lore.kernel.org/linux-cve-announce/2026062555-CVE-2026-53183-a7a3@gregkh/T