Attack Surface Reduction bypass via malicious file
Published Feb 14, 2023 · Updated Aug 19, 2026
Security feature bypass in Microsoft Defender Security Intelligence Updates before 1.379.200.0 allows local users to evade ASR blocking. The affected detection logic fails to enforce an Attack Surface Reduction block when a malicious file is opened; Microsoft has not disclosed the faulty rule or parser operation. Exploitation requires a user to open the malicious file, after which the file proceeds without the intended ASR block.
Summary
What happened
Security feature bypass in Microsoft Defender Security Intelligence Updates before 1.379.200.0 allows local users to evade ASR blocking. The affected detection logic fails to enforce an Attack Surface Reduction block when a malicious file is opened; Microsoft has not disclosed the faulty rule or parser operation. Exploitation requires a user to open the malicious file, after which the file proceeds without the intended ASR block.
The record
- CVE
- CVE-2023-21809
- Published
- Feb 14, 2023
- Updated
- Aug 19, 2026
- Vendor
- Microsoft
- Product
- Microsoft Defender Security Intelligence Updates
- Classifications
- T1204.002
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 14, 2023CVE publishedPublication date reported by the CVE source.
- Aug 19, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.0.0 <1.379.200.0
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
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo