SYSTEM privilege escalation via update-path TOCTOU
Published Apr 14, 2026 · Updated Apr 14, 2026
Insufficient access control in Microsoft Defender Antimalware Platform before 4.18.26030.3011 allows local users to gain SYSTEM privileges. The update import path trusts a previously checked location after oplocks suspend Defender, letting a user redirect its privileged read into a Volume Shadow Copy of the SAM hive. Low-privilege Windows access and a pending update are required; successful exploitation exposes credential hashes and permits SYSTEM process execution.
Summary
What happened
Insufficient access control in Microsoft Defender Antimalware Platform before 4.18.26030.3011 allows local users to gain SYSTEM privileges. The update import path trusts a previously checked location after oplocks suspend Defender, letting a user redirect its privileged read into a Volume Shadow Copy of the SAM hive. Low-privilege Windows access and a pending update are required; successful exploitation exposes credential hashes and permits SYSTEM process execution.
The record
- CVE
- CVE-2026-33825
- Published
- Apr 14, 2026
- Updated
- Apr 14, 2026
- Vendor
- Microsoft
- Product
- Microsoft Defender Antivirus Antimalware Platform
- Classifications
- CWE-1220, T1003.002, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 10, 2026Exploitation reportedBlueHammer activity during a live intrusion
- Apr 14, 2026CVE publishedPublication date reported by the CVE source.
- Apr 14, 2026Record updatedLatest update available in the CVE record.
- Apr 22, 2026Exploitation reportedCISA Known Exploited Vulnerabilities listing
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=4.0.0.0 <4.18.26030.3011
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
- BlueHammerweaponized · validated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- BlueHammer activity during a live intrusionreported exploitation
- CISA Known Exploited Vulnerabilities listingknown exploited catalog
Technologies
Your stack
See the directory against your own environment.
Your stack
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