CVE-2026-80585

CVE CVE-2026-80585EUVD EUVD-2026-66500Published 2026-08-26T14:37:40.000ZLast changed 2026-08-27T05:02:06.000ZCVSS 9.4

What the advisory describes

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".

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

Linux — Linux 6.2; patch: 6.18.46; patch: 7.2; 36b122baf6a8bd46b4a591f12f4ed17b22257408 <fca7e444c04689fe4cc6b56f2725f804a4bb1ef9; patch: 6.12.105; 36b122baf6a8bd46b4a591f12f4ed17b22257408 <e00b63056fb4f261455b3e5df5268a1f8ce47a87; 36b122baf6a8bd46b4a591f12f4ed17b22257408 <75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5; patch: 6.6.153; 36b122baf6a8bd46b4a591f12f4ed17b22257408 <f75f174edc865738522e514d042cf5627f084859; patch: 7.1.10; patch: 0; 36b122baf6a8bd46b4a591f12f4ed17b22257408 <72b4a0c51a4b550d40301d60a366b429b8c8e78d

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

Linux — Linux

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