Bug 2464396 (CVE-2026-31708)

Summary: CVE-2026-31708 kernel: smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Server Message Block (SMB) client. A malicious server can exploit an out-of-bounds read vulnerability by manipulating the OutputBufferLength during a QUERY_INFO operation. This can lead to the exposure of sensitive kernel memory to userspace, resulting in information disclosure.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-05-01 15:04:25 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path

smb2_ioctl_query_info() has two response-copy branches: PASSTHRU_FSCTL
and the default QUERY_INFO path.  The QUERY_INFO branch clamps
qi.input_buffer_length to the server-reported OutputBufferLength and then
copies qi.input_buffer_length bytes from qi_rsp->Buffer to userspace, but
it never verifies that the flexible-array payload actually fits within
rsp_iov[1].iov_len.

A malicious server can return OutputBufferLength larger than the actual
QUERY_INFO response, causing copy_to_user() to walk past the response
buffer and expose adjacent kernel heap to userspace.

Guard the QUERY_INFO copy with a bounds check on the actual Buffer
payload.  Use struct_size(qi_rsp, Buffer, qi.input_buffer_length)
rather than an open-coded addition so the guard cannot overflow on
32-bit builds.
Comment 1 Keith Grant 2026-05-01 20:07:19 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026050121-CVE-2026-31708-f27c@gregkh/T