CVE-2026-98686
Received Received - Intake

SMB Client File Extension Pagecache Exposure in Linux Kernel

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

Description
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.

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Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98686
EUVD
EUVD-2026-103940

Affected Vendors & Products

Showing 5 associated CPEs
Vendor Product Version / Range
Linux Linux 72c419d9b073628d3b5b0b2fc787b724f1a8c726
Linux Linux 72c419d9b073628d3b5b0b2fc787b724f1a8c726
Linux Linux 72c419d9b073628d3b5b0b2fc787b724f1a8c726
Linux Linux 72c419d9b073628d3b5b0b2fc787b724f1a8c726
Linux Linux 5.1

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves the SMB client incorrectly handling file extensions. When a file is extended via zero range, the system fails to properly discard cached data beyond the original end of the file. This can expose previously written data that should have been hidden after the file size increase.

Detection Guidance

This vulnerability is specific to the Linux kernel's SMB client implementation and does not have a direct network detection method. Check if your system is running a vulnerable kernel version with uname -a. Look for signs of unexpected file content changes in SMB-mounted files.

Impact Analysis

If you use SMB shares on a Linux system with this kernel vulnerability, sensitive data that was previously written to a file via memory-mapped operations might become visible after the file is extended. This could lead to unintended information disclosure to unauthorized users accessing the file.

Compliance Impact

This vulnerability could violate data protection requirements under GDPR or HIPAA by exposing sensitive information stored in files. Organizations may fail compliance audits if unauthorized access to personal or health data occurs due to improper file handling in SMB shares.

Mitigation Strategies

Update your Linux kernel to the latest patched version. If immediate patching is not possible, avoid using SMB file operations that extend files via zero range until the update is applied.

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