VulnSocial

CVE-2026-80585Patch

LOWCVSS 9.4 · CRITICAL

Signal is active with 2 mentions in latest observed window

Immediate actions

  • Patch affected systems immediately

Recommended action window: Monitor and triage in normal cycle

NVD 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".

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0.5/ 10 priority

Sources & remediation

Other references

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

AVAILABLE

Momentum

STABLE

Threat summary

  • Patch or workaround signal is available
  • 3 mentions across 2 observed days
  • Momentum state: stable

What's happening

  • Patch or workaround mentioned in 1 signal
  • Technical details provided in 3 signals
  • Disclosure: 1 classified signal
  • Peaked at 2 mentions on most recent observed day (2026-08-27)
  • 3 total mentions across 2 days

Deep dive

Activity timeline3 mentions / 2d
01122Mentions · 2026-08-26: 1Mentions · 2026-08-27: 2Patch / Workaround · 2026-08-27: 1Technical Details · 2026-08-26: 1Technical Details · 2026-08-27: 208-2608-27
Signal classification2 categories
Patch
266.7%
Disclosure
133.3%
Referenced assets3 URLs
Classification over time
DateTotalLabels
2026-08-261
Patch1
2026-08-272
Disclosure1Patch1
Full discourse3 posts
  • Infoflowcloud@infoflowcloud
    Disclosure

    🚨*CVE* CVE-2026-80585 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-co… https://www.cve.org/CVERecord?id=CVE-2026-80585 ----- Traducción: CVE-2026-80585 En … https://infoflow.cloud`

    Post summary

    The post announces that CVE-2026-80585, affecting the Linux kernel MPTCP fastopen path, has been resolved, but provides no PoC, exploit code, or evidence of active exploitation.

    0000063
    102 followersView on X
  • CVE@CVEnew
    Patch

    CVE-2026-80585 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-co… https://www.cve.org/CVERecord?id=CVE-2026-80585

    Post summary

    CVE-2026-80585 in the Linux kernel has been addressed with a patch, resolving the Fast Open subflow marking issue.

    00000758
    58.0K followersView on X
  • Vulmon Vulnerability Feed@VulmonFeeds
    Patch

    CVE-2026-80585 Linux Kernel MPTCP Fastopen State Confusion Bug Resolved https://vulmon.com/vulnerabilitydetails?qid=CVE-2026-80585

    Post summary

    The post announces that CVE‑2026‑80585, a Linux Kernel MPTCP Fastopen State Confusion bug, has been resolved, though it lacks detailed patch or technical exploitation information.

    0000097
    4.1K followersView on X

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