CVE-20XX-?
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CVE-2026-80585

9.4 CRITICAL 0.3% exploit odds No fix listed Other OS & kernel

What it is

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".

At a glance

Exploitability
Can be exploited over the network without logging in. High risk of data tampering, service disruption.
Exploit odds
0.3% chance of exploitation in the next 30 days (EPSS).
Fix
No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

  1. ReservedThe CVE id was reserved by its CNA
  2. PublishedDisclosed publicly on CVE.org and NVD
  3. Last updatedMost recent change to the record

Why it ranks here

Details

Published
Last modified
Exploit probability
0.3% · EPSS, next 30 days
Record status
Received

Attack profile CVSS 3.1 · 9.4

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
High
Raw vector

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

Is it in your code?

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Read https://cve-list.com/agent/cve/CVE-2026-80585.md and follow it. Check whether this project is affected by CVE-2026-80585. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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References

NVD record · CVE.org record