What is CVE-2026-80585?

CVE-2026-80585 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.4 out of 10, affecting Linux kernel versions from 6.2 onward and patched in 6.6.153, 6.12.105, 6.18.46 and others. CVE-2026-80585 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-80585?

CVE-2026-80585 has a CVSS score of 9.4 out of 10, rated Critical severity. The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H.

Is there a patch available for CVE-2026-80585?

Yes, CVE-2026-80585 has been patched. Fixed versions include 6.6.153, 6.12.105, 6.18.46 and others. If you are running Linux kernel 6.2 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-80585 actively exploited?

CVE-2026-80585 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

CVE-2026-80585

Critical

In the Linux kernel, the following vulnerability has been resolved: mptcp: fastopen: only mark MPTFO subflows with SYN data Passive TCP Fast Open accepts a valid-cookie SYN even when it carries no data. In that case the child socket's receive queue is intentionally left empty. mptcp_fastopen_subflow_synack_set_params() set is_mptfo before checking for queued SYN data. That made data-less TFO SYNs hit a WARN and, if the warning was non-fatal, left stale MPTFO state behind. The stale flag could later trigger a state-confusion bug in check_fully_established(). Only mark the subflow as MPTFO after confirming that an SKB was queued. Return quietly when the receive queue is empty. Note that mptcp_subflow_context's is_mptfo field is now not just about subflows where the TFO was present, but about MPTFO subflow that consumed SYN data. Only having a valid cookie but not carrying data is not really "doing TFO".

Package Linux Kernel

Published 2026-08-26

Last modified 2026-08-27

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

9.4

out of 10

Critical

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

High

Availability

High

Vector string

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

Affected versions

Linux kernel versions 6.2 and later are affected. Fixed in 6.6.153, 6.12.105, 6.18.46, 7.1.10, 7.2 and their respective stable series.

Affected from

≥ 6.2

Fixed in

✓ 6.6.153 6.6.x ✓ 6.12.105 6.12.x ✓ 6.18.46 6.18.x ✓ 7.1.10 7.1.x ✓ 7.2

References

5 total

Details

CVE ID CVE-2026-80585

Severity Critical

CVSS score 9.4 / 10

CVSS version 3.1

Published 2026-08-26

Modified 2026-08-27

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-80585?

CVE-2026-80585 is a Critical severity Linux kernel vulnerability with a CVSS score of 9.4 out of 10 . It affects Linux kernel versions from 6.2 onward and has been patched in 6.6.153, 6.12.105, 6.18.46 and others. CVE-2026-80585 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-80585?

CVE-2026-80585 has a CVSS score of 9.4 out of 10, rated Critical severity (CVSS 3.1). The vector string is CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H.
Is there a patch available for CVE-2026-80585?

Yes. CVE-2026-80585 has been patched. Fixed versions include 6.6.153, 6.12.105, 6.18.46 and others. If you are running Linux kernel 6.2 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-80585 actively exploited?

No. CVE-2026-80585 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.