Bug 2568620 (CVE-2026-99273)

Summary: CVE-2026-99273 kernel: kernel: ksmbd: Denial of Service via out-of-bounds write in get_file_stream_info()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
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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Doc Text:
A flaw was found in the Linux kernel's ksmbd Server Message Block (SMB) server. When preparing file stream information, the server does not account for a terminating character during response buffer size checks, leading to a two-byte out-of-bounds write. A remote attacker could exploit this flaw by issuing file stream queries that fill the response buffer, causing memory corruption that may result in a system crash (Denial of Service) or potential arbitrary code execution.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-11-07 14:21:31 UTC 
In the Linux kernel, the following vulnerability has been resolved:

ksmbd: reserve space for the UTF-16 terminator in stream info

smb_strtoUTF16() always writes a terminating zero UTF-16 unit after the
converted characters, but get_file_stream_info() budgets only
sizeof(struct smb2_file_stream_info) + streamlen * 2 for a stream entry
and sizeof(struct smb2_file_stream_info) + 7 * 2 for the trailing
"::$DATA" entry. When an entry exactly fills the 448-byte small response
buffer, the terminator is written two bytes past the allocation.

Reserve one extra UTF-16 unit in both budget checks. The terminator is
not part of the wire format, so the reported lengths are unchanged.