CVE-2026-80585Network attack vectorHinoki check available

Kernel state corruption via stale MPTFO flag

Published Aug 26, 2026 · Updated Aug 27, 2026

State confusion in the Linux kernel allows remote attackers to corrupt MPTCP connection state through crafted TCP segments. The mptcp_fastopen_subflow_synack_set_params() function sets is_mptfo before confirming that a data-bearing SYN queued an SKB, leaving stale state for check_fully_established(). An exposed MPTCP listener with TCP Fast Open server mode enabled is required; successful triggers can corrupt handshake state, reset connections, or panic hosts configured with panic_on_warn.

CVSS severity9.4
Critical
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

State confusion in the Linux kernel allows remote attackers to corrupt MPTCP connection state through crafted TCP segments. The mptcp_fastopen_subflow_synack_set_params() function sets is_mptfo before confirming that a data-bearing SYN queued an SKB, leaving stale state for check_fully_established(). An exposed MPTCP listener with TCP Fast Open server mode enabled is required; successful triggers can corrupt handshake state, reset connections, or panic hosts configured with panic_on_warn.

The record

CVE
CVE-2026-80585
Published
Aug 26, 2026
Updated
Aug 27, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-367, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=36b122baf6a8bd46b4a591f12f4ed17b22257408 <72b4a0c51a4b550d40301d60a366b429b8c8e78d
  2. Affected versionversion=36b122baf6a8bd46b4a591f12f4ed17b22257408 <75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5
  3. Affected versionversion=36b122baf6a8bd46b4a591f12f4ed17b22257408 <e00b63056fb4f261455b3e5df5268a1f8ce47a87
  4. Affected versionversion=36b122baf6a8bd46b4a591f12f4ed17b22257408 <f75f174edc865738522e514d042cf5627f084859
  5. Affected versionversion=36b122baf6a8bd46b4a591f12f4ed17b22257408 <fca7e444c04689fe4cc6b56f2725f804a4bb1ef9
  6. Affected versionversion=6.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=36b122baf6a8bd46b4a591f12f4ed17b22257408 <72b4a0c51a4b550d40301d60a366b429b8c8e78d; version=36b122baf6a8bd46b4a591f12f4ed17b22257408 <75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5; version=36b122baf6a8bd46b4a591f12f4ed17b22257408 <e00b63056fb4f261455b3e5df5268a1f8ce47a87; version=36b122baf6a8bd46b4a591f12f4ed17b22257408 <f75f174edc865738522e514d042cf5627f084859; version=36b122baf6a8bd46b4a591f12f4ed17b22257408 <fca7e444c04689fe4cc6b56f2725f804a4bb1ef9; version=6.2

Published CVSS scores

9.4Linux kernel CVE teamCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
7.0Red HatCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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