Detect CVE-2026-33825 - Microsoft Defender Insufficient Access Control Exploitation in CrowdStrike LogScale
Detects exploitation attempts targeting CVE-2026-33825, an insufficient granularity of access control vulnerability (CWE-1220) in Microsoft Defender. This KEV-listed vulnerability allows attackers to bypass Defender access controls, potentially disabling protections, modifying exclusions, or tampering with security configurations without appropriate privilege levels.
MITRE ATT&CK
LogScale Detection Query
#event_simpleName IN (ProcessRollup2, SyntheticProcessRollup2, RegistryOperationDetectInfo, DirectoryOperationDetectInfo)
| case {
#event_simpleName IN (ProcessRollup2, SyntheticProcessRollup2):
ImageFileName LIKE~ "%powershell.exe"
AND CommandLine LIKE~ "%Set-MpPreference%"
AND (
CommandLine LIKE~ "%DisableRealtimeMonitoring%"
OR CommandLine LIKE~ "%ExclusionPath%"
OR CommandLine LIKE~ "%ExclusionProcess%"
OR CommandLine LIKE~ "%DisableBehaviorMonitoring%"
OR CommandLine LIKE~ "%DisableIOAVProtection%"
)
AND UserIsAdmin != "1";
#event_simpleName IN (ProcessRollup2, SyntheticProcessRollup2):
ImageFileName LIKE~ "%sc.exe"
AND CommandLine LIKE~ "%WinDefend%"
AND (
CommandLine LIKE~ "%stop%"
OR CommandLine LIKE~ "%disable%"
OR CommandLine LIKE~ "%delete%"
)
AND UserSid != "S-1-5-18";
#event_simpleName = "RegistryOperationDetectInfo":
RegObjectName LIKE~ "%Windows Defender%"
AND RegOperationType IN ("CREATE", "SET", "DELETE")
AND UserSid NOT IN ("S-1-5-18", "S-1-5-19") ;
}
| eval TamperType = case(
ImageFileName LIKE~ "%powershell.exe" AND CommandLine LIKE~ "%Set-MpPreference%", "PowerShell_Defender_Config_Change",
ImageFileName LIKE~ "%sc.exe", "Service_Stop_Disable",
#event_simpleName = "RegistryOperationDetectInfo", "Registry_Tamper",
true(), "Unknown"
)
| stats count() AS EventCount, values(CommandLine) AS Commands, values(RegObjectName) AS RegistryTargets, values(TamperType) AS TamperTypes, min(timestamp) AS FirstSeen, max(timestamp) AS LastSeen BY aid, UserName, ComputerName
| where EventCount >= 1
| sort -LastSeenCrowdStrike Falcon LogScale (CQL) query detecting Defender tamper activity via process events (PowerShell Set-MpPreference abuse, sc.exe service manipulation) and registry modification events targeting Windows Defender configuration keys, consistent with CVE-2026-33825 access control bypass.
Data Sources
Required Tables
False Positives & Tuning
- CrowdStrike Falcon sensor itself adjusting Defender settings for co-existence during initial deployment
- IT administrators with elevated privileges performing authorized Defender policy remediation
- MDM-enrolled endpoints receiving Defender configuration policy pushes from Intune or SCCM
- Automated vulnerability remediation scripts legitimately reconfiguring Defender after patch application
Other platforms for CVE-2026-33825
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Disable Defender Real-Time Monitoring via PowerShell (CVE-2026-33825 Simulation)
Expected signal: Sysmon EventID 1 (process creation) for powershell.exe with CommandLine containing Set-MpPreference and DisableRealtimeMonitoring; Windows Defender Operational EventID 5001 (real-time protection disabled); DeviceProcessEvents in MDE showing the PowerShell invocation
- Test 2Add Defender Exclusion Path via PowerShell
Expected signal: Sysmon EventID 1 for powershell.exe with Add-MpPreference and ExclusionPath in CommandLine; Defender Operational EventID 5007 (configuration changed) with new exclusion path; registry modification to HKLM\SOFTWARE\Microsoft\Windows Defender\Exclusions\Paths
- Test 3Stop WinDefend Service via sc.exe
Expected signal: Sysmon EventID 1 (process creation) for sc.exe with CommandLine 'sc stop WinDefend'; Windows System EventID 7036 (WinDefend service stopped); Security EventID 4689 (process exit) for MsMpEng.exe if service fully stops; Defender Operational EventID 5001
- Test 4Modify Defender Registry Key to Disable Antispyware
Expected signal: Sysmon EventID 13 (registry value set) with TargetObject HKLM\SOFTWARE\Policies\Microsoft\Windows Defender\DisableAntiSpyware and Details=DWORD (0x00000001); Security EventID 4657 for registry write to Defender policy key; Defender Operational EventID 5007
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