Privileged microcode execution via insecure signature hashing
Published Jun 27, 2025 · Updated Feb 26, 2026
Improper signature verification in AMD Zen-based processor ROM loaders allows local users with administrator privilege to execute malicious microcode. The loader uses an insecure hash function during RSA signature validation, allowing forged signatures for arbitrary microcode patches. Administrative access is required; successful exploitation can corrupt x86 instruction semantics and compromise privileged data and SMM execution.
Summary
What happened
Improper signature verification in AMD Zen-based processor ROM loaders allows local users with administrator privilege to execute malicious microcode. The loader uses an insecure hash function during RSA signature validation, allowing forged signatures for arbitrary microcode patches. Administrative access is required; successful exploitation can corrupt x86 instruction semantics and compromise privileged data and SMM execution.
The record
- CVE
- CVE-2024-36347
- Published
- Jun 27, 2025
- Updated
- Feb 26, 2026
- Vendor
- Advanced Micro Devices, Inc.
- Product
- AMD Ryzen™ 7000 Series Desktop Processors
- Classifications
- CWE-347, T1542.001
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Jun 27, 2025CVE publishedPublication date reported by the CVE source.
- Feb 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?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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
- EntrySign RDRAND microcode patch proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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