CVE-2026-98686: smb: client: discard post-EOF pagecache when extending a file via zero range
In the Linux kernel, the following vulnerability has been resolved:
smb: client: discard post-EOF pagecache when extending a file via zero range
smb3zerorange() 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.12.113-1 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 7.2.10-1 - Upgrade
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debian/linux-6.12to a version that resolves this vulnerability.Fixed in 6.12.113-1~deb12u1 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 5.15.224 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.1.191 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.6.160 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.12.113 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 6.18.56 - Upgrade
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linux/Kernelto a version that resolves this vulnerability.Fixed in 7.2.10 - Upgrade
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debian/linuxto a version that resolves this vulnerability.Fixed in 6.12.115-2Fixed in 7.2.12-1Fixed in 7.2.15-1 - Upgrade
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azurelinux/kernelto a version that resolves this vulnerability.Fixed in 6.6.161.1-1
Event History
Frequently Asked Questions
Who is exposed to this issue?
Systems using the Linux kernel SMB client are exposed when a file is extended through the SMB zero-range operation and cached data exists beyond the file's previous EOF. The affected cached data may have been dirtied past EOF through an mmap.
What conditions are required for unintended data to become visible?
A folio straddling the old EOF must retain data past EOF, and the file must subsequently be extended via smb3_zero_range(). Because the post-EOF page cache was not discarded, that retained data can become visible as file content after extension.
How is the issue addressed?
The fix changes the page-cache discard boundary to the smaller of the zero-range offset and the old EOF, ensuring cached data past the previous EOF is discarded when the operation extends the file.