Kernel warnings via unchecked shadow-stack fault bits
Published Oct 28, 2026 · Updated Oct 28, 2026
Out-of-bounds reads in Linux 6.18 KVM allow guest OS users to trigger kernel warnings via shadow-stack page faults on AMD hosts. The permission_fault() function retains the unexpected SS error-code bit when deriving an index into its 16-entry permissions table, producing an out-of-range read. Triggering requires guest shadow-stack activity reaching the affected host fault handler; reported outcomes are kernel warnings and UBSAN reports, not demonstrated data disclosure or code execution.
Summary
What happened
Out-of-bounds reads in Linux 6.18 KVM allow guest OS users to trigger kernel warnings via shadow-stack page faults on AMD hosts. The permission_fault() function retains the unexpected SS error-code bit when deriving an index into its 16-entry permissions table, producing an out-of-range read. Triggering requires guest shadow-stack activity reaching the affected host fault handler; reported outcomes are kernel warnings and UBSAN reports, not demonstrated data disclosure or code execution.
The record
- CVE
- CVE-2026-99120
- Published
- Oct 28, 2026
- Updated
- Oct 28, 2026
- Vendor
- The Linux Kernel Organization
- Product
- Linux
- Classifications
- Unavailable
- Attack vector
- local
- Privileges
- Unavailable
Timeline
How it unfolded
- Oct 28, 2026CVE publishedPublication date reported by the CVE source.
- Oct 28, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=6.18
- Affected versionversion=8db428fd5229ba509d515af10d7f33d7d4a54bfe <0caeefed99b37f03251a00eb1fdb403a1cf2cb68
- Affected versionversion=8db428fd5229ba509d515af10d7f33d7d4a54bfe <d6e08ec2fff45e0ec69f11010851650d7c6282b9
- Affected versionversion=8db428fd5229ba509d515af10d7f33d7d4a54bfe <e90ab3669181c6469e3647ef2b30ae408275f496
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
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Public exploit references
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Technologies
Your stack
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Your stack
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