From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2CE974483B7 for ; Wed, 26 Aug 2026 14:41:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787755295; cv=none; b=ZmtedwWlN33rw1aDSqmr0Yx6h9O+YUNlrfBxFuwTWtSMC7zclfGcyOlFd7UYy/ttKhlPqVgHzaejAREO3b0zTEvIKI05hLgy0mcXOtqYkmKZDpQ5CCFi9FzDi9UhKAUoasJ3yS0EDErbNW1qZ9RtGe/wN5RFtU1SdNBUVODMlbY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787755295; c=relaxed/simple; bh=WnFxmRww6nuFKGIzW1uiAwT/bXyp+0DNNLR5+InWQSM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=CGH1Q/nRFTRtNfwqcxdVU93vCrE5bLq4Bc7Msy0yP/eGqVPYIkjZcmCXzAiJSUggwh3lnTIWYrL2tax298k13RDVGu1uQIAqShhS3O6iS0bDB0fyxIgDujLw5XiN9iJso1vVJQwEYj4r81+2vYVMw8neVQwU60p9PdwNXtU8jrk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=GtHkZuR7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="GtHkZuR7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4EEB31F00AC4; Wed, 26 Aug 2026 14:41:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1787755291; bh=psT84HD1TVeOy1UsuzPMpJmJ7FKJzO7EfbINH9P6MDw=; h=From:To:Cc:Subject:Date:Reply-To; b=GtHkZuR7koBi1vdl+iT+LS5IDyh+UHt1F3/ul3oAaeEMSruJnTaK13Pb4yJ4aSXXn BUzV6gJFIGUULoyxlZPiMMNmvvB9scqlJ0d2VjizvpFGBNRNh5BchPozPH/A0BsOkd Ae6KQWJw6CHl89oaLD2GDAbuMgGWh32t2eQ2N4sY= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-80585: mptcp: fastopen: only mark MPTFO subflows with SYN data Date: Wed, 26 Aug 2026 16:38:21 +0200 Message-ID: <2026082616-CVE-2026-80585-8682@gregkh> X-Mailer: git-send-email 2.55.0 Reply-To: , Precedence: bulk X-Mailing-List: linux-cve-announce@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3250; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=QWSyGfznKHxwnohtrfASF2N9P9uKAhn7yFl93ZzHNhA=; b=owGbwMvMwCRo6H6F97bub03G02pJDFl9v2RKbiSsW1XxYNLsp6eZA5c/UXH2mxkf5ZUrevHCh 0ni0dYVHbEsDIJMDLJiiixftvEc3V9xSNHL0PY0zBxWJpAhDFycAjCRh+cZ5te7/Jy7h7PMwsNL fve7uSbTJVLM4hnm+0lqfZkauIjnXJzuhrdJKr8KJ+YkAgA= X-Developer-Key: i=gregkh@linuxfoundation.org; a=openpgp; fpr=F4B60CC5BF78C2214A313DCB3147D40DDB2DFB29 Content-Transfer-Encoding: 8bit From: Greg Kroah-Hartman Description =========== 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". The Linux kernel CVE team has assigned CVE-2026-80585 to this issue. Affected and fixed versions =========================== Issue introduced in 6.2 with commit 36b122baf6a8bd46b4a591f12f4ed17b22257408 and fixed in 6.6.153 with commit f75f174edc865738522e514d042cf5627f084859 Issue introduced in 6.2 with commit 36b122baf6a8bd46b4a591f12f4ed17b22257408 and fixed in 6.12.105 with commit fca7e444c04689fe4cc6b56f2725f804a4bb1ef9 Issue introduced in 6.2 with commit 36b122baf6a8bd46b4a591f12f4ed17b22257408 and fixed in 6.18.46 with commit 75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5 Issue introduced in 6.2 with commit 36b122baf6a8bd46b4a591f12f4ed17b22257408 and fixed in 7.1.10 with commit 72b4a0c51a4b550d40301d60a366b429b8c8e78d Issue introduced in 6.2 with commit 36b122baf6a8bd46b4a591f12f4ed17b22257408 and fixed in 7.2 with commit e00b63056fb4f261455b3e5df5268a1f8ce47a87 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-80585 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: net/mptcp/fastopen.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/f75f174edc865738522e514d042cf5627f084859 https://git.kernel.org/stable/c/fca7e444c04689fe4cc6b56f2725f804a4bb1ef9 https://git.kernel.org/stable/c/75e564b2ced1cc3d9a8904c7d2d2bb448fffb8b5 https://git.kernel.org/stable/c/72b4a0c51a4b550d40301d60a366b429b8c8e78d https://git.kernel.org/stable/c/e00b63056fb4f261455b3e5df5268a1f8ce47a87