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 8EE8D175A64 for ; Fri, 15 May 2026 05:17:39 +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=1778822259; cv=none; b=t4r6UM93bnQIo/PHmJXsMOD33F8+uYXY630X7ie1nmsvXfubJ9bCZKxLZUdQ3t5LGcdAQnsGLaq01JU9SA87+gVtyd+4rv8h33tke4YOnyfT4C7wZVVZCRSB8I/TygtmOaTtXKEWV4H0Mn9HdJhOEucn499+sYlQpbZS4knYgBM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778822259; c=relaxed/simple; bh=qBNUU+w5Mp6bxysTMEGC2XL9ZsSncMdBNNsHoFKJB64=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=ltqazy8grN+FQtHpEPQFv6kjqqgdI9Mf9R7qXwZ6sJkQB5gRE4KXWzp3XRiojfHX3zin82Y621Vka1HPY9+Nh65xOBsDaQmV/bo+QspJufSsdB2UMa8aa0mnftJMkNxRKRHhOFR6gFEdQ/Zn1kvV2C7tYQobJZZw7/tvwU/omTI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=lQg8gnhq; 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="lQg8gnhq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5AA4C2BCB0; Fri, 15 May 2026 05:17:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1778822259; bh=qBNUU+w5Mp6bxysTMEGC2XL9ZsSncMdBNNsHoFKJB64=; h=From:To:Cc:Subject:Date:Reply-To:From; b=lQg8gnhq0SxnMcfqCLx9P46Lfv9uG4JJ7FXGe0HPO2bmx0BZ4d53GrXFHpD1Cc+1/ zDdrD93/LO67a6f4NSLNsULLRXN5MKG2LKBYIsGwad7TVi8Ki4jIAenfmvlzdlK6wM MkFPSDuDyhUj3Ukl/QxsePlgyCnGtoFXE5g2oQIM= From: Greg Kroah-Hartman To: linux-cve-announce@vger.kernel.org Cc: Greg Kroah-Hartman Subject: CVE-2026-43490: ksmbd: validate inherited ACE SID length Date: Fri, 15 May 2026 07:17:40 +0200 Message-ID: <2026051539-CVE-2026-43490-43c5@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=3197; i=gregkh@linuxfoundation.org; h=from:subject:message-id; bh=Gg/Is1uqIcvcXrU4/l2aAtkqL4f+BqijRlN9OxuRC7o=; b=owGbwMvMwCRo6H6F97bub03G02pJDFlsa0q+cti0c6nG1GTnq1ayhhTWr0hbp2t6w3SmmnfCu rk6JZEdsSwMgkwMsmKKLF+28RzdX3FI0cvQ9jTMHFYmkCEMXJwCMJHZ3xkWHOo68efqsv68tdfv HijjFcuKWPkkh2GuGCsz85VWtYptHQaJrgdz5LNu3vgIAA== 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: validate inherited ACE SID length smb_inherit_dacl() walks the parent directory DACL loaded from the security descriptor xattr. It verifies that each ACE contains the fixed SID header before using it, but does not verify that the variable-length SID described by sid.num_subauth is fully contained in the ACE. A malformed inheritable ACE can advertise more subauthorities than are present in the ACE. compare_sids() may then read past the ACE. smb_set_ace() also clamps the copied destination SID, but used the unchecked source SID count to compute the inherited ACE size. That could advance the temporary inherited ACE buffer pointer and nt_size accounting past the allocated buffer. Fix this by validating the parent ACE SID count and SID length before using the SID during inheritance. Compute the inherited ACE size from the copied SID so the size matches the bounded destination SID. Reject the inherited DACL if size accumulation would overflow smb_acl.size or the security descriptor allocation size. The Linux kernel CVE team has assigned CVE-2026-43490 to this issue. Affected and fixed versions =========================== Issue introduced in 5.15 with commit e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and fixed in 6.12.88 with commit 47c6e37a77b10e74f70d845ba4ea5d3cafa00336 Issue introduced in 5.15 with commit e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and fixed in 6.18.30 with commit 1aa60fea7f637c071f529ad6784aecca2f2f0c5f Issue introduced in 5.15 with commit e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and fixed in 7.0.7 with commit c1d95c995d5bcb24b639200a899eda59cb1e6d64 Issue introduced in 5.15 with commit e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9 and fixed in 7.1-rc3 with commit 996454bc0da84d5a1dedb1a7861823087e01a7ae 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-2026-43490 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/smbacl.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/47c6e37a77b10e74f70d845ba4ea5d3cafa00336 https://git.kernel.org/stable/c/1aa60fea7f637c071f529ad6784aecca2f2f0c5f https://git.kernel.org/stable/c/c1d95c995d5bcb24b639200a899eda59cb1e6d64 https://git.kernel.org/stable/c/996454bc0da84d5a1dedb1a7861823087e01a7ae