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 Details
- CVSS 3.1 Base Score: 9.4
- CVSS 3.1 Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade kernel6.18-headersUpgrade kernel6.18-debuginfo-common-aarch64Upgrade perf6.18-debuginfoUpgrade kernel6.18-tools-debuginfoUpgrade python3-perf6.18-debuginfoUpgrade bpftool6.18-debuginfoUpgrade kernel-livepatch-6.18.48-107.148Upgrade kernel6.18-debuginfoUpgrade bpftool6.18Upgrade kernel6.18-tools-develUpgrade kernel6.18-debuginfo-common-x86_64Upgrade kernel6.18-modules-extraUpgrade kernel6.18Upgrade kernel6.18-develUpgrade kernel6.18-toolsUpgrade python3-perf6.18Upgrade microvm-kernel6.18Upgrade kernel6.18-modules-extra-commonUpgrade perf6.18 | Sep 30, 2026 | Aug 26, 2026 |
| Debian | — | Upgrade linuxUpgrade linux-6.12 | Aug 27, 2026 | Aug 27, 2026 |
| Redhat_linux | — | No solution exists | Aug 31, 2026 | Aug 26, 2026 |
| Ubuntu | — | Upgrade linux-image-nvidia-tegraUpgrade linux-image-nvidia-tegra-6.8Upgrade linux-image-nvidia-tegra-rtUpgrade linux-image-6.8.0-1036-nvidia-tegra-rtUpgrade linux-image-6.8.0-1036-nvidia-tegraUpgrade linux-image-nvidia-tegra-rt-6.8 | Oct 7, 2026 | Oct 6, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Sep 15, 2026 | Aug 26, 2026 |
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