Privilege escalation via incomplete L2 operand encoding
Published Aug 11, 2026 · Updated Aug 11, 2026
Incorrect calculation in Intel TDX Guest software before 0.3.1 allows local users with high privileges to escalate privilege. The enter_l2_vcpu function constructs an encoded RCX operand from the L2 VM index and invalidation mode but passes only the unshifted index to TDG.VP.ENTER. Exploitation requires privileged system software inside a TDX guest, no user interaction, and access to the Ring 3 API; successful use weakens confidentiality, integrity, and availability only within the vulnerable system.
Summary
What happened
Incorrect calculation in Intel TDX Guest software before 0.3.1 allows local users with high privileges to escalate privilege. The enter_l2_vcpu function constructs an encoded RCX operand from the L2 VM index and invalidation mode but passes only the unshifted index to TDG.VP.ENTER. Exploitation requires privileged system software inside a TDX guest, no user interaction, and access to the Ring 3 API; successful use weakens confidentiality, integrity, and availability only within the vulnerable system.
The record
- CVE
- CVE-2026-20763
- Published
- Aug 11, 2026
- Updated
- Aug 11, 2026
- Vendor
- Topcon Positioning Systems, Inc.
- Product
- Intel TDX Guest software
- Classifications
- CWE-682, CAPEC-128, T1068
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Aug 11, 2026CVE publishedPublication date reported by the CVE source.
- Aug 11, 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?
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- Affected versionversion=before version 0.3.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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