CVE-2026-63867: mptcp: close TOCTOU race while computing rcv_wnd
In the Linux kernel, the following vulnerability has been resolved:
mptcp: close TOCTOU race while computing rcvwnd
The MPTCP output path access locklessly the MPTCP-level ackseq in multiple times, using possibly different values for the dataack 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.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-63867?
The severity of CVE-2026-63867 is high with a score of 8.2.
How do I fix CVE-2026-63867?
To fix CVE-2026-63867, update to the latest version of the Linux kernel where the vulnerability has been resolved.
What does CVE-2026-63867 affect?
CVE-2026-63867 affects the Linux kernel, specifically the MPTCP implementation.
What kind of vulnerability is CVE-2026-63867?
CVE-2026-63867 is a Time of Check to Time of Use (TOCTOU) race condition vulnerability.
Is CVE-2026-63867 related to data security?
Yes, CVE-2026-63867 can potentially affect data integrity due to its nature as a race condition.