mptcp: fastopen: only mark MPTFO subflows with SYN data

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-80585
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-26 15:17:14 UTC
Updated2026-08-27 06:17:45 UTC
DescriptionIn 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".

Risk And Classification

Primary CVSS: v3.1 9.4 CRITICAL from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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

EPSS: 0.003170000 probability, percentile 0.239660000 (date 2026-08-27)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary9.4CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H
3.1CNADECLARED9.4CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 36b122baf6a8bd46b4a591f12f4ed17b22257408 f75f174edc865738522e514d042cf5627f084859 git Not specified
CNA Linux Linux affected 36b122baf6a8bd46b4a591f12f4ed17b22257408 fca7e444c04689fe4cc6b56f2725f804a4bb1ef9 git Not specified
CNA Linux Linux affected 36b122baf6a8bd46b4a591f12f4ed17b22257408 75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5 git Not specified
CNA Linux Linux affected 36b122baf6a8bd46b4a591f12f4ed17b22257408 72b4a0c51a4b550d40301d60a366b429b8c8e78d git Not specified
CNA Linux Linux affected 36b122baf6a8bd46b4a591f12f4ed17b22257408 e00b63056fb4f261455b3e5df5268a1f8ce47a87 git Not specified
CNA Linux Linux affected 6.2 Not specified
CNA Linux Linux unaffected 6.2 semver Not specified
CNA Linux Linux unaffected 6.6.153 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.105 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.46 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.10 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/72b4a0c51a4b550d40301d60a366b429b8c8e78d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/e00b63056fb4f261455b3e5df5268a1f8ce47a87 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/f75f174edc865738522e514d042cf5627f084859 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/fca7e444c04689fe4cc6b56f2725f804a4bb1ef9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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