SEPTEMBER 8, 2026
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Case File

CVE-2026-63867

HIGH · CVSS 8.2 EPSS 0.32%

Source: NVD + CISA KEV + EPSS · Published 2026-07-19 · Last synced 2026-08-18

CyberRota Analysis

AI-Generated

The vulnerability affects the Linux kernel's implementation of MultiPath TCP (MPTCP), where a time-of-check to time-of-use (TOCTOU) race condition can lead to inconsistencies in the acknowledgment sequence and the announced receive window. This flaw could allow an attacker to exploit the MPTCP protocol, potentially leading to data corruption or denial of service. Organizations using Linux systems with MPTCP enabled should prioritize patching this vulnerability to mitigate the risk of exploitation.

CVE
CVE-2026-63867
Severity
HIGH
CVSS
8.2
EPSS
0.32%
Linux

Original NVD Description

In the Linux kernel, the following vulnerability has been resolved: mptcp: close TOCTOU race while computing rcv_wnd The MPTCP output path access locklessly the MPTCP-level ack_seq in multiple times, using possibly different values for the data_ack in the DSS option and to compute the announced rcv wnd for the same packet. Refactor the cote to avoid inconsistencies which may confuse the peer. Also ensure that the MPTCP level rcv wnd is updated only when the egress packet actually contains a DSS ack.