Measured-boot bypass via inconsistent ELAM hive parsing
Published Apr 13, 2021 · Updated Aug 3, 2024
Security feature bypass in Microsoft Windows ELAM allows local administrators to evade measured-boot validation by altering its registry hive. The Windows loader measures a malformed hive without checking subkey order, while the kernel later enforces order and deletes a measured key before ELAM uses it. Administrative access is required to modify the offline hive; exploitation lets removed ELAM signature data escape measured-boot attestation.
Summary
What happened
Security feature bypass in Microsoft Windows ELAM allows local administrators to evade measured-boot validation by altering its registry hive. The Windows loader measures a malformed hive without checking subkey order, while the kernel later enforces order and deletes a measured key before ELAM uses it. Administrative access is required to modify the offline hive; exploitation lets removed ELAM signature data escape measured-boot attestation.
The record
- CVE
- CVE-2021-27094
- Published
- Apr 13, 2021
- Updated
- Aug 3, 2024
- Vendor
- Microsoft
- Product
- Windows 10 Version 1507
- Classifications
- T1562.001
- Attack vector
- local
- Privileges
- admin
Timeline
How it unfolded
- Apr 13, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record 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=10.0.0 <publication
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
- Measured Boot and Malware Signatures ELAM hive proofproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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