CVE-2026-80585

Last refreshed2026-10-17

Status: UPDATED | Advisory ID: CVE-2026-80585

Key Details

CVE	CVE-2026-80585
CVSS Score / Version	9.4 (Critical) / CVSS v3.1
Updated	2026-10-16
CVSS Vector	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H`
CVSS Prose	attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is low; integrity impact is high; availability impact is high.
Affected products	Linux Kernel

Vendor	Product	Affected Versions	Patch Status
Linux	Linux Kernel

Vendor

Product

Affected Versions

Patch Status

Linux

Linux Kernel

Subsystems	OT Supporting Infrastructure
Sectors	All Sectors

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". (NVD)

Monitor Linux's web page for any future patch releases.

Source	Reference
NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-80585
CVE	https://www.cve.org/CVERecord?id=CVE-2026-80585

Source

Reference

NVD

CVE