CVE-2026-98681: smb: client: split cifsFileInfo bitfields to avoid shared-byte RMW races
In the Linux kernel, the following vulnerability has been resolved:
smb: client: split cifsFileInfo bitfields to avoid shared-byte RMW races
The invalidHandle, swapfile, oplockbreakcancelled, offload, and statusfiledeleted fields are stored in the same bitfield byte in struct cifsFileInfo, but are updated in different code paths that may run simultaneously, and are protected by different locks. Since bitfield assignments generate byte-level read-modify-write operations, a modification to one flag can overwrite a concurrent modification to another flag.
To avoid these races, convert these flags from a bitfield to separate bool fields.
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 5.10.273 - 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
Which Linux systems are relevant to this issue?
The issue is in the Linux kernel SMB client, specifically in struct cifsFileInfo. Systems that do not use the kernel SMB client are not implicated by the provided information.
What condition causes the race?
Several cifsFileInfo flags share one bitfield byte but are updated by different code paths under different locks. Concurrent updates can perform overlapping byte-level read-modify-write operations, allowing one flag update to overwrite another.
What is the available remediation?
The resolved change separates invalidHandle, swapfile, oplock_break_cancelled, offload, and status_file_deleted into individual bool fields, eliminating the shared-byte bitfield updates. The provided stable-kernel commit references identify the fixes.