Bug 2555073 (CVE-2026-98686)

Summary: CVE-2026-98686 kernel: smb: client: discard post-EOF pagecache when extending a file via zero range
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
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 SMB (Server Message Block) client. When extending a file using a zero-range operation, cached memory pages past the previous end-of-file boundary are not properly discarded. A local user can exploit this vulnerability to view stale or previously buffered data that becomes exposed as valid file content, resulting in an information disclosure.
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Description OSIDB Bzimport 2026-10-18 15:52:54 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: discard post-EOF pagecache when extending a file via zero range

smb3_zero_range() removed the pagecache only for the range being zeroed,
so when it extends the file the folio straddling the old EOF - which may
hold data dirtied past EOF through an mmap - was never dropped and became
visible as file content once the file was extended.

Lower the discard boundary to the smaller of the zero-range offset and the
old EOF.
Comment 1 Mauro Matteo Cascella 2026-10-22 03:04:13 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98686.mbox