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 E754D58B6B5 for ; Fri, 11 Sep 2026 19:57:32 +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=1789156666; cv=none; b=ut1W3rwRup0UgwI7N0onJOcE2CNY4qptpgSU/wjTt00vhGYVmBVahQ3tUTx8uMdSqdR0E5b/Z9MyXohRICT5RAsc4XVLjUOGlEB7aWy9hF96kR2MJPaOsGGeVRb+Rm9lZzFlTKjV3vrys6eCrrF3jgYCXiLKCX9aPXs3whwfNVo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789156666; c=relaxed/simple; bh=V6X5CepXboXz7/6xxm7EUPAsjgvEXYgHs17mnvN/gEE=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=HSN/6W0XZSPr5iQ/2OOzk3gMIqKlpL6R2L8P8LWFXVe5XCKhLP6JL8EVAAL49USZAgChzo0nfmCXtKzGCGeuQTA1iijtvpdNYZcPqO/2DIk0CrYr21jbD7DwjpVu+obdVsGfMFjEsEkqN6aHO72tpBehdbWv9g6lwOsfeGdquvs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Z+rXdX1e; 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="Z+rXdX1e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4E7951F00893; Fri, 11 Sep 2026 19:57:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1789156651; bh=+Qk6QtPGCbYMAzRkzwTul9xIxHyFM7cuXv3C1wNASa4=; h=From:To:Cc:Subject:Date:Reply-To; b=Z+rXdX1engALEMaSgnvVg3Pku0OFcks+iRKdc+ZPZHglqoGkFPfLRNjGX+kPq4IO1 lVoESQpJ1Xe+ng4dApdQZJ89IfX7BtFnbf8mcjByvDAsJLT0chd7S9lBnMDqZW5iPk 5S3Z5S3CpDNROyCF/b38uAjJikZDaG4GRZDf4MCU= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-89554: mptcp: fix uninitialized local_id in syncookie MP_JOIN reconstruction Date: Fri, 11 Sep 2026 21:44:03 +0200 Message-ID: <2026091122-CVE-2026-89554-cd26@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=3023; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=AH8pzXob6xJpBFkDqr10TEeWfEmr5p+VElo/JjE92Yw=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlLIpN+KbhIhH2wsYoIsznV6PVrntyhk/O3Rnb5Ly866 s+qxnO4I5aFQZCJQVZMkeXLNp6j+ysOKXoZ2p6GmcPKBDKEgYtTACaS388wP/XE1ir9XZVax9pv H68uuaHqIZJYyDA/xyR43vSu4F2G/q6izDdkpK4qOVoBAA== 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: fix uninitialized local_id in syncookie MP_JOIN reconstruction mptcp_token_join_cookie_init_state() restores remote_nonce, local_nonce, backup, join_id, token and msk from the saved cookie entry when rebuilding the request socket for a MP_JOIN 4th-ACK handled under SYN cookies, but it does not restore local_id, even though the SYN path saved it. subflow_ulp_clone() then reads that uninitialized field and stores it as the joined subflow's address-ID. Because the request-sock slab is SLAB_TYPESAFE_BY_RCU and not zeroed on allocation, the value is the stale byte of a previously freed request socket, which an off-path peer can influence by sending concurrent MP_JOIN SYNs. This corrupts the path manager's id-based subflow bookkeeping for the connection. Restore subflow_req->local_id from the cookie entry, as done for the other fields. The Linux kernel CVE team has assigned CVE-2026-89554 to this issue. Affected and fixed versions =========================== Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.12.109 with commit 64f2c5dd49b956a542c8c02b8dad5d262a462bba Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 6.18.50 with commit 51887ccd88791ddaa8755a7c614fda031ecf7982 Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 7.2.4 with commit bf19d166337c6488b39cb03eeeffb30a941d6326 Issue introduced in 5.9 with commit 9466a1ccebbe54ac57fb8a89c2b4b854826546a8 and fixed in 7.3-rc1 with commit b878dfdd12d7a5b8722a78d35e313506140ca3d9 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-2026-89554 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/syncookies.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/64f2c5dd49b956a542c8c02b8dad5d262a462bba https://git.kernel.org/stable/c/51887ccd88791ddaa8755a7c614fda031ecf7982 https://git.kernel.org/stable/c/bf19d166337c6488b39cb03eeeffb30a941d6326 https://git.kernel.org/stable/c/b878dfdd12d7a5b8722a78d35e313506140ca3d9