Bug 2568632 (CVE-2026-99272)

Summary: CVE-2026-99272 kernel: kernel: out-of-bounds read in SMB client via crafted read response
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Server Message Block (SMB) client. The SMB2 read handler does not properly validate whether the data range specified by the server fits within the boundaries of the received packet. A malicious SMB server could exploit this vulnerability by sending a crafted read response with an invalid data offset and length, triggering an out-of-bounds memory read. This issue can lead to a system crash, resulting in a Denial of Service (DoS), or potentially expose sensitive kernel memory.
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Description OSIDB Bzimport 2026-11-07 14:22:14 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: validate the data area in SMB2_read()

SMB2_read() copies le32_to_cpu(rsp->DataLength) bytes from
(char *)rsp + rsp->DataOffset without checking that the range lies
within the response actually received. A READ response with
DataOffset == 0 makes smb2_get_data_area_len() zero the data length, so
smb2_check_message() accepts a frame as short as the fixed response,
while SMB2_read() still uses the server-supplied DataLength, capped only
by CIFS_MAX_MSGSIZE and the caller's length.

A malicious server can answer the synchronous read used by the
mfsymlinks (or SFU) symlink parser with an 81-byte READ response
carrying DataOffset 0 and DataLength 1067, making the client copy 1067
bytes from a 448-byte receive object (KASAN slab-out-of-bounds; up to
16 KiB in the general case).

Clamp a zero (or header-overlapping) DataOffset to read_rsp_size, as
handle_read_data() does for the asynchronous path, and reject the
response unless DataOffset + DataLength fits within rsp_iov.iov_len.
The SMB1 helper was fixed the same way in 5be5bdda5863.