Measured-boot bypass via unparsed ELAM big data
Published Apr 13, 2021 · Updated Nov 19, 2024
Security feature bypass in Microsoft Windows allows local users with administrator rights to alter ELAM data without changing measured-boot results. The Windows loader's OslGetBinaryValue routine treats CM_BIG_DATA metadata as value bytes instead of consolidating ELAM values larger than 16,344 bytes. Exploitation requires administrator access to modify the unmounted ELAM hive and can let corrupted or downgraded antimalware signatures retain expected measurements.
Summary
What happened
Security feature bypass in Microsoft Windows allows local users with administrator rights to alter ELAM data without changing measured-boot results. The Windows loader's OslGetBinaryValue routine treats CM_BIG_DATA metadata as value bytes instead of consolidating ELAM values larger than 16,344 bytes. Exploitation requires administrator access to modify the unmounted ELAM hive and can let corrupted or downgraded antimalware signatures retain expected measurements.
The record
- CVE
- CVE-2021-28447
- Published
- Apr 13, 2021
- Updated
- Nov 19, 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.
- Nov 19, 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
- BI.ZONE ELAM CM_BIG_DATA reproductionproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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