Time-of-check Time-of-use (TOCTOU) Affecting kernel-modules-core package, versions *


Severity

Recommended
medium

Based on Red Hat Enterprise Linux security rating.

Threat Intelligence

EPSS
0.32% (24th percentile)

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  • Snyk IDSNYK-RHEL10-KERNELMODULESCORE-19388646
  • published28 Aug 2026
  • disclosed26 Aug 2026

Introduced: 26 Aug 2026

NewCVE-2026-80585  (opens in a new tab)
CWE-367  (opens in a new tab)

How to fix?

There is no fixed version for RHEL:10 kernel-modules-core.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-modules-core package and not the kernel-modules-core package as distributed by RHEL. See How to fix? for RHEL:10 relevant fixed versions and status.

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".

CVSS Base Scores

version 3.1