CVE-2026-80585
9.4 · CRITICALOverview
CVE-2026-80585 is a critical-severity vulnerability. It was published on August 26, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).
This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
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".
Remediation
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
References
Frequently Asked Questions
What is CVE-2026-80585?
CVE-2026-80585 is a critical-severity vulnerability. It was published on August 26, 2026 and has a CVSS 3.1 base score of 9.4 (CRITICAL).
How severe is CVE-2026-80585?
This vulnerability has a CVSS 3.1 base score of 9.4, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2026-80585?
Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2026-80585?
CyberStrike's AI-powered security agents can automatically detect CVE-2026-80585 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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