mptcp: fastopen: only mark MPTFO subflows with SYN data
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".
CVE-2026-80585
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-80585
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "36b122baf6a8bd46b4a591f12f4ed17b22257408",
"lessThan": "f75f174edc865738522e514d042cf5627f084859",
"versionType": "git"
},
{
"status": "affected",
"version": "36b122baf6a8bd46b4a591f12f4ed17b22257408",
"lessThan": "fca7e444c04689fe4cc6b56f2725f804a4bb1ef9",
"versionType": "git"
},
{
"status": "affected",
"version": "36b122baf6a8bd46b4a591f12f4ed17b22257408",
"lessThan": "75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5",
"versionType": "git"
},
{
"status": "affected",
"version": "36b122baf6a8bd46b4a591f12f4ed17b22257408",
"lessThan": "72b4a0c51a4b550d40301d60a366b429b8c8e78d",
"versionType": "git"
},
{
"status": "affected",
"version": "36b122baf6a8bd46b4a591f12f4ed17b22257408",
"lessThan": "e00b63056fb4f261455b3e5df5268a1f8ce47a87",
"versionType": "git"
}
],
"programFiles": [
"net/mptcp/fastopen.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.2"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.2",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.153",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.105",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.46",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.10",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"net/mptcp/fastopen.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-80585
Source reference:
/cveMetadata/cveId
Publisher severity
critical
Source reference: /containers/cna/metrics
- Event
- #34333 · Revision 1
- Added to Heist Feed
- Publisher date