Privileged message forgery via HMAC timing discrepancy
Published Jun 26, 2026 · Updated Jun 26, 2026
Observable timing discrepancy in AMD Secure Processor firmware on affected Ryzen processors allows local users to forge authenticated messages. The ASP exposes input-dependent timing while validating hash message authentication codes, enabling repeated guesses to produce a valid code. High local privileges and a high-complexity attack are required; successful exploitation accepts arbitrary message input and compromises integrity.
Summary
What happened
Observable timing discrepancy in AMD Secure Processor firmware on affected Ryzen processors allows local users to forge authenticated messages. The ASP exposes input-dependent timing while validating hash message authentication codes, enabling repeated guesses to produce a valid code. High local privileges and a high-complexity attack are required; successful exploitation accepts arbitrary message input and compromises integrity.
The record
- CVE
- CVE-2023-20540
- Published
- Jun 26, 2026
- Updated
- Jun 26, 2026
- Vendor
- Advanced Micro Devices, Inc.
- Product
- AMD Ryzen™ Threadripper™ PRO 5000 WX-Series Processors
- Classifications
- CWE-208
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Jun 26, 2026CVE publishedPublication date reported by the CVE source.
- Jun 26, 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?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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