CVE-2026-63867

mptcp: close TOCTOU race while computing rcv_wnd

State: Published
Severity: 8.2 High
Published: Jul 19, 2026
Updated: Oct 19, 2026
Reserved: Jul 19, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	8.2 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H	Linux

Weaknesses

CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Affected Products

Product	Versions
LinuxLinux	fa3fe2b150316b294f2c662653501273ff25bba8 to before 301a33fd590c408a05c5df800e0cc1e6a8a2f8f8Affected fa3fe2b150316b294f2c662653501273ff25bba8 to before 68364963e5baf03f16b4420292291f75c8f66497Affected fa3fe2b150316b294f2c662653501273ff25bba8 to before 907ac6b1658e0277f979fcdfae2a753b495c1510Affected fa3fe2b150316b294f2c662653501273ff25bba8 to before c4f4cf60797974873dbc8e100144682a6f2f861fAffected fa3fe2b150316b294f2c662653501273ff25bba8 to before 3b8cbba7c0ed31189c89f90be247b8973ffa79efAffected fa3fe2b150316b294f2c662653501273ff25bba8 to before 8f4f0a157e8436a05bf8c3670b24dbc258911c43Affected fa3fe2b150316b294f2c662653501273ff25bba8 to before 8ab24fdebc369c0dfb90f82c1650b1e66662bb45Affected
LinuxLinux	5.11Affected before 5.11Not affected 5.15.210 through 5.15.Not affected 6.1.176 through 6.1.Not affected 6.6.143 through 6.6.Not affected 6.12.94 through 6.12.Not affected 6.18.36 through 6.18.Not affected 7.0.13 through 7.0.Not affected 7.1 and laterNot affected

Product

Versions

LinuxLinux

fa3fe2b150316b294f2c662653501273ff25bba8 to before 301a33fd590c408a05c5df800e0cc1e6a8a2f8f8Affected
fa3fe2b150316b294f2c662653501273ff25bba8 to before 68364963e5baf03f16b4420292291f75c8f66497Affected
fa3fe2b150316b294f2c662653501273ff25bba8 to before 907ac6b1658e0277f979fcdfae2a753b495c1510Affected
fa3fe2b150316b294f2c662653501273ff25bba8 to before c4f4cf60797974873dbc8e100144682a6f2f861fAffected
fa3fe2b150316b294f2c662653501273ff25bba8 to before 3b8cbba7c0ed31189c89f90be247b8973ffa79efAffected
fa3fe2b150316b294f2c662653501273ff25bba8 to before 8f4f0a157e8436a05bf8c3670b24dbc258911c43Affected
fa3fe2b150316b294f2c662653501273ff25bba8 to before 8ab24fdebc369c0dfb90f82c1650b1e66662bb45Affected

LinuxLinux

5.11Affected
before 5.11Not affected
5.15.210 through 5.15.*Not affected
6.1.176 through 6.1.*Not affected
6.6.143 through 6.6.*Not affected
6.12.94 through 6.12.*Not affected
6.18.36 through 6.18.*Not affected
7.0.13 through 7.0.*Not affected
7.1 and laterNot affected

References

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