From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 E1F093F0ABA for ; Fri, 8 May 2026 14:27:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778250441; cv=none; b=ftxJ9ZvdKtpoAElVwcJEmsJ5vCgNnIxBxf4rl3GRrPanifhz0bpDZCGL5ldNCEcNkcMCs04xab8hPdSnj+UawqSsCGokd6TjdrqpPaq/joxH7Z0YEh4u93OGwSomh9GovK1OLeaZEr32tUO5uZ1+M673dcY4KEXxmOh6keqzvpY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778250441; c=relaxed/simple; bh=HbeQHj5k+DNykTrs8Iz36pBd7LbdPk1/2bonbXxwfPM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=IhrvcZAbgwJcxfhYtJdpwmdVKR7gn49WDOuI/f4qTTx2T6mlBRhDVOKR4pYswcgyM91s5kAKsqKjziQEQDkocTW6dGJ5y1A21asOYpXy6P86HoPV533ENeAL1Zu21LKcr72eqA1XUdDJnLMttUr7/JTV6d2nLQ0Xf+yHdGOc3gU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=de30f5vX; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="de30f5vX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42D8FC2BCB0; Fri, 8 May 2026 14:27:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778250440; bh=HbeQHj5k+DNykTrs8Iz36pBd7LbdPk1/2bonbXxwfPM=; h=From:To:Cc:Subject:Date:Reply-To:From; b=de30f5vXGcgwN2SKJ9vDsixGGNB6eLN94420VJlw/nUcXtzQJVPn/vi4HPUX90/84 LfG4JBy+AoUIgOupJgJQagNp1w1aCv+BmSy4G7N/foqLWfB9fzp5KKbspqBPgjb4BL va602kxEnXPwOiWZgS8tnSESaLcPI1RpWipI38X8= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-43455: mctp: route: hold key->lock in mctp_flow_prepare_output() Date: Fri, 8 May 2026 16:23:04 +0200 Message-ID: <2026050859-CVE-2026-43455-3fb2@gregkh> X-Mailer: git-send-email 2.54.0 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=4141; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=oXK9b7mpmmXxObQQg00e0A4yk30SsXLIBzssVHA4W/U=; b=owGbwMvMwCRo6H6F97bub03G02pJDJl/P7b/sCj7MsnKpLcs2StqqYrSSa3wjTeTpjn9m8X1+ n/i7/+KHbEsDIJMDLJiiixftvEc3V9xSNHL0PY0zBxWJpAhDFycAjCRwECGufL1bdlGFwyvc17e sejyvQ1WuuEPrjIsWFKjb1X467HYiqTz+VL9rt9kv8+dBgA= 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: mctp: route: hold key->lock in mctp_flow_prepare_output() mctp_flow_prepare_output() checks key->dev and may call mctp_dev_set_key(), but it does not hold key->lock while doing so. mctp_dev_set_key() and mctp_dev_release_key() are annotated with __must_hold(&key->lock), so key->dev access is intended to be serialized by key->lock. The mctp_sendmsg() transmit path reaches mctp_flow_prepare_output() via mctp_local_output() -> mctp_dst_output() without holding key->lock, so the check-and-set sequence is racy. Example interleaving: CPU0 CPU1 ---- ---- mctp_flow_prepare_output(key, devA) if (!key->dev) // sees NULL mctp_flow_prepare_output( key, devB) if (!key->dev) // still NULL mctp_dev_set_key(devB, key) mctp_dev_hold(devB) key->dev = devB mctp_dev_set_key(devA, key) mctp_dev_hold(devA) key->dev = devA // overwrites devB Now both devA and devB references were acquired, but only the final key->dev value is tracked for release. One reference can be lost, causing a resource leak as mctp_dev_release_key() would only decrease the reference on one dev. Fix by taking key->lock around the key->dev check and mctp_dev_set_key() call. The Linux kernel CVE team has assigned CVE-2026-43455 to this issue. Affected and fixed versions =========================== Issue introduced in 5.16 with commit 67737c457281dd199ceb9e31b6ba7efd3bfe566d and fixed in 6.1.167 with commit 47893166bc5611ee9a20de6b8d2933b2320fb772 Issue introduced in 5.16 with commit 67737c457281dd199ceb9e31b6ba7efd3bfe566d and fixed in 6.6.130 with commit 86f5334fcb48a5b611c33364ab52ca684d0f6d91 Issue introduced in 5.16 with commit 67737c457281dd199ceb9e31b6ba7efd3bfe566d and fixed in 6.12.78 with commit 0695712f3a6f1a48915f95767cfb42077683dcdc Issue introduced in 5.16 with commit 67737c457281dd199ceb9e31b6ba7efd3bfe566d and fixed in 6.18.19 with commit 925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f Issue introduced in 5.16 with commit 67737c457281dd199ceb9e31b6ba7efd3bfe566d and fixed in 6.19.9 with commit 8d27d9b260dd19c1b519e1a13de6448f9984e30e Issue introduced in 5.16 with commit 67737c457281dd199ceb9e31b6ba7efd3bfe566d and fixed in 7.0 with commit 7d86aa41c073c4e7eb75fd2e674f1fd8f289728a 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-2026-43455 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/mctp/route.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/47893166bc5611ee9a20de6b8d2933b2320fb772 https://git.kernel.org/stable/c/86f5334fcb48a5b611c33364ab52ca684d0f6d91 https://git.kernel.org/stable/c/0695712f3a6f1a48915f95767cfb42077683dcdc https://git.kernel.org/stable/c/925a5ffd99cddd7a7e41d5ad120c7a2c6d50260f https://git.kernel.org/stable/c/8d27d9b260dd19c1b519e1a13de6448f9984e30e https://git.kernel.org/stable/c/7d86aa41c073c4e7eb75fd2e674f1fd8f289728a