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 ADA4D3EC6B2 for ; Sat, 15 Aug 2026 12:29:59 +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=1786797000; cv=none; b=X3MrMKmxfdNUx6gKk/DGlKib2nSsC7jV/tyem6IXFt9S4lV1abaYschmu1YwfO4vsqcYsN1dr5WTROdprngAYgsccobVTuJ/sxEMtDcScD05pZmZY0xx3yEjUwTVwdwk0xcBNXuA5XNzIiPqcp/aqeCLW8N+lFdYkaU40J8nyi0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786797000; c=relaxed/simple; bh=xhDhwsb0bDCpOypQgEJHzWkzxnZZH/N31aIiQqJTdiU=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=mRT+kh0iyjhDF1o2IeKiyS7TM8sS+UVQDI5ewZdSOi+eLHoF3U8AXZWRil+8tDufvWqBujnvxuQeLhZE0tSJtbq3Nh5+OVu1f7Fe+3HB/QLdTWLR58IJv1ogsAGQIScvDtO3s63u3DferK0AN8qGPe05TSzCD/SHm4gm7VOxSu8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=0IlhWbP/; 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="0IlhWbP/" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 131C11F000E9; Sat, 15 Aug 2026 12:29:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786796999; bh=Ef9XsARX6OX0OMy0g35JBt9FBSBQ+JRK7c0AAur9VoQ=; h=From:To:Cc:Subject:Date:Reply-To; b=0IlhWbP/p7DHvSE5terpFGD0i0nRCGY4HXqaEHd2aL/lNat3LE4u/PW9aULMSGRSA dqMGo0FUiPKPsBS0eV+RlSuWTJSfKetfFyxjzy+JGHTjQMVCJ6fvoybAYkEEAzwTXu Zx1P4a8/AOrA+cjmXNdRlFJZbpFtSfSBWpRnuzLk= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-74494: ksmbd: reject repeated SMB2 NEGOTIATE requests Date: Sat, 15 Aug 2026 21:26:15 +0900 Message-ID: <2026081539-CVE-2026-74494-751d@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=3168; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=CDMDMBl1Si2qyksfnSmzpcnH9HgNF+Z21C9wxxj8dW8=; b=owGbwMvMwCRo6H6F97bub03G02pJDFkNUYe3sIWUmae3T7lxV0jgU86De+/EZxxd32TX71FqO ulMyMc3HbEsDIJMDLJiiixftvEc3V9xSNHL0PY0zBxWJpAhDFycAjCRObwMcyW2z/4WcvO9bv39 ExO7DrQ/fVpfnc0wv7DmqMz9RZMZXygEzha1bxNOWblxIgA= 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: ksmbd: reject repeated SMB2 NEGOTIATE requests Unauthenticated client can send multiple successful SMB2 NEGOTIATE requests on one connection before SESSION_SETUP. While the connection is in KSMBD_SESS_NEED_SETUP, smb2_handle_negotiate() accepts another SMB3.1.1 NEGOTIATE and overwrites conn->preauth_info with a new allocation. Only the final allocation is freed when the connection is released, leaking one object for every additional successful request. A repeated SMB2 NEGOTIATE after a dialect has been selected is a protocol violation. MS-SMB2 section 3.3.5.4 requires the server to disconnect without replying in this case. Set the connection exiting when rejecting the request, in addition to suppressing the response. Reject SMB2 NEGOTIATE unless the connection is new or is waiting for the SMB2 NEGOTIATE that follows an SMB1 multi-protocol negotiate. Serialize both SMB1 and SMB2 negotiation paths under conn->srv_mutex, since they update connection-wide dialect and negotiation state. Move the locking contract to ksmbd_smb_negotiate_common(), where the state and dialect are selected, and add ksmbd_conn_new() for consistent state access. The Linux kernel CVE team has assigned CVE-2026-74494 to this issue. Affected and fixed versions =========================== Issue introduced in 5.15 with commit e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and fixed in 6.18.44 with commit a60b5da05e318d9a364dbac38c347c7f24e625e7 Issue introduced in 5.15 with commit e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and fixed in 7.1.8 with commit 7e02cb30e8a1f5fc78cb10b220b06020e36d0bbe Issue introduced in 5.15 with commit e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and fixed in 7.2-rc6 with commit cb469993b3a61a72653770856d37af616d72d05f 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-2026-74494 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: fs/smb/server/connection.h fs/smb/server/smb2pdu.c fs/smb/server/smb_common.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/a60b5da05e318d9a364dbac38c347c7f24e625e7 https://git.kernel.org/stable/c/7e02cb30e8a1f5fc78cb10b220b06020e36d0bbe https://git.kernel.org/stable/c/cb469993b3a61a72653770856d37af616d72d05f