CVE-2026-63867
mptcp: close TOCTOU race while computing rcv_wnd
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.
INFO
Published Date :
July 19, 2026, 3:16 p.m.
Last Modified :
July 19, 2026, 3:16 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Affected Products
The following products are affected by CVE-2026-63867
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Update the Linux kernel to the latest version.
- Apply MPTCP-specific patches if available.
- Ensure MPTCP rcv_wnd updates are consistent.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-63867.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-63867 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-63867
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-63867 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-63867 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Jul. 19, 2026
Action Type Old Value New Value Added Affected [{'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': 'fa3fe2b150316b294f2c662653501273ff25bba8', 'lessThan': '301a33fd590c408a05c5df800e0cc1e6a8a2f8f8', 'versionType': 'git'}, {'status': 'affected', 'version': 'fa3fe2b150316b294f2c662653501273ff25bba8', 'lessThan': '68364963e5baf03f16b4420292291f75c8f66497', 'versionType': 'git'}, {'status': 'affected', 'version': 'fa3fe2b150316b294f2c662653501273ff25bba8', 'lessThan': '907ac6b1658e0277f979fcdfae2a753b495c1510', 'versionType': 'git'}, {'status': 'affected', 'version': 'fa3fe2b150316b294f2c662653501273ff25bba8', 'lessThan': 'c4f4cf60797974873dbc8e100144682a6f2f861f', 'versionType': 'git'}, {'status': 'affected', 'version': 'fa3fe2b150316b294f2c662653501273ff25bba8', 'lessThan': '3b8cbba7c0ed31189c89f90be247b8973ffa79ef', 'versionType': 'git'}, {'status': 'affected', 'version': 'fa3fe2b150316b294f2c662653501273ff25bba8', 'lessThan': '8f4f0a157e8436a05bf8c3670b24dbc258911c43', 'versionType': 'git'}, {'status': 'affected', 'version': 'fa3fe2b150316b294f2c662653501273ff25bba8', 'lessThan': '8ab24fdebc369c0dfb90f82c1650b1e66662bb45', 'versionType': 'git'}], 'programFiles': ['net/mptcp/options.c'], 'defaultStatus': 'unaffected'}, {'repo': 'https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git', 'vendor': 'Linux', 'product': 'Linux', 'versions': [{'status': 'affected', 'version': '5.11'}, {'status': 'unaffected', 'version': '0', 'lessThan': '5.11', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '5.15.210', 'versionType': 'semver', 'lessThanOrEqual': '5.15.*'}, {'status': 'unaffected', 'version': '6.1.176', 'versionType': 'semver', 'lessThanOrEqual': '6.1.*'}, {'status': 'unaffected', 'version': '6.6.143', 'versionType': 'semver', 'lessThanOrEqual': '6.6.*'}, {'status': 'unaffected', 'version': '6.12.94', 'versionType': 'semver', 'lessThanOrEqual': '6.12.*'}, {'status': 'unaffected', 'version': '6.18.36', 'versionType': 'semver', 'lessThanOrEqual': '6.18.*'}, {'status': 'unaffected', 'version': '7.0.13', 'versionType': 'semver', 'lessThanOrEqual': '7.0.*'}, {'status': 'unaffected', 'version': '7.1', 'versionType': 'original_commit_for_fix', 'lessThanOrEqual': '*'}], 'programFiles': ['net/mptcp/options.c'], 'defaultStatus': 'affected'}] Added 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. Added Reference https://git.kernel.org/stable/c/301a33fd590c408a05c5df800e0cc1e6a8a2f8f8 Added Reference https://git.kernel.org/stable/c/3b8cbba7c0ed31189c89f90be247b8973ffa79ef Added Reference https://git.kernel.org/stable/c/68364963e5baf03f16b4420292291f75c8f66497 Added Reference https://git.kernel.org/stable/c/8ab24fdebc369c0dfb90f82c1650b1e66662bb45 Added Reference https://git.kernel.org/stable/c/8f4f0a157e8436a05bf8c3670b24dbc258911c43 Added Reference https://git.kernel.org/stable/c/907ac6b1658e0277f979fcdfae2a753b495c1510 Added Reference https://git.kernel.org/stable/c/c4f4cf60797974873dbc8e100144682a6f2f861f