What is CVE-2026-63867?

CVE-2026-63867 is a High severity Linux kernel vulnerability with a CVSS score of 8.2 out of 10, affecting Linux kernel versions from 5.11 onward and patched in 5.15.210, 6.1.176, 6.6.143 and others. CVE-2026-63867 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-63867?

CVE-2026-63867 has a CVSS score of 8.2 out of 10, rated High severity. The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H.

Is there a patch available for CVE-2026-63867?

Yes, CVE-2026-63867 has been patched. Fixed versions include 5.15.210, 6.1.176, 6.6.143 and others. If you are running Linux kernel 5.11 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-63867 actively exploited?

CVE-2026-63867 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-63867

High

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.

Package Linux Kernel

Published 2026-07-19

Last modified 2026-07-27

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

8.2

out of 10

High

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

High

Vector string

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H

Affected versions

Linux kernel versions 5.11 and later are affected. Fixed in 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13, 7.1 and their respective stable series.

Affected from

≥ 5.11

Fixed in

✓ 5.15.210 5.15.x ✓ 6.1.176 6.1.x ✓ 6.6.143 6.6.x ✓ 6.12.94 6.12.x ✓ 6.18.36 6.18.x ✓ 7.0.13 7.0.x ✓ 7.1

References

7 total

Showing 5 of 7 references View all on NVD

Details

CVE ID CVE-2026-63867

Severity High

CVSS score 8.2 / 10

CVSS version 3.1

Published 2026-07-19

Modified 2026-07-27

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-63867?

CVE-2026-63867 is a High severity Linux kernel vulnerability with a CVSS score of 8.2 out of 10 . It affects Linux kernel versions from 5.11 onward and has been patched in 5.15.210, 6.1.176, 6.6.143 and others. CVE-2026-63867 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-63867?

CVE-2026-63867 has a CVSS score of 8.2 out of 10, rated High severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H.
Is there a patch available for CVE-2026-63867?

Yes. CVE-2026-63867 has been patched. Fixed versions include 5.15.210, 6.1.176, 6.6.143 and others. If you are running Linux kernel 5.11 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-63867 actively exploited?

No. CVE-2026-63867 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.