Detect Microsoft Defender Denial of Service Vulnerability (CVE-2026-45498) in CrowdStrike LogScale
CVE-2026-45498 is a Denial of Service vulnerability in Microsoft Defender. Exploitation can cause Defender to crash, hang, or become unresponsive, effectively disabling endpoint protection on affected hosts. This vulnerability is listed in the CISA Known Exploited Vulnerabilities catalog, indicating active exploitation in the wild. Attackers may leverage this to disable security tooling prior to follow-on intrusion activity.
MITRE ATT&CK
- Tactic
- Defense Evasion Impact
LogScale Detection Query
#event_simpleName IN ("ProcessRollup2", "ServiceStarted", "ServiceStopped")
| filter ImageFileName CONTAINS "MsMpEng" OR ServiceDisplayName CONTAINS "Defender" OR ServiceDisplayName CONTAINS "Windows Defender"
| eval event_type=case(
event_simpleName="ProcessRollup2" AND ImageFileName CONTAINS "MsMpEng", "DefenderProcessEvent",
event_simpleName="ServiceStopped" AND ServiceDisplayName CONTAINS "Defender", "DefenderServiceStopped",
event_simpleName="ServiceStarted" AND ServiceDisplayName CONTAINS "Defender", "DefenderServiceStarted",
true(), "Other"
)
| stats count() AS event_count, dc(event_simpleName) AS event_type_variety, min(timestamp) AS first_event, max(timestamp) AS last_event BY aid, ComputerName, event_type
| where event_count >= 3 AND event_type_variety >= 2
| eval time_window_secs = last_event - first_event
| where time_window_secs <= 3600
| sort -event_countCrowdStrike CQL query detecting repeated Microsoft Defender process and service lifecycle events that may indicate CVE-2026-45498 DoS exploitation. Identifies hosts with multiple Defender service stop/start cycles within a one-hour window.
Data Sources
Required Tables
False Positives & Tuning
- CrowdStrike Falcon sensor interactions with Defender causing service events
- Windows Update applying Defender definition or engine updates
- IT administrators performing endpoint security assessment tasks
- Automated vulnerability scanning tools triggering service state queries
Other platforms for CVE-2026-45498
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 1Simulate Defender Real-Time Protection Disable Event
Expected signal: Windows Defender Operational EventID 5001 (disabled) followed by EventID 5000 (enabled); DeviceEvents ActionType AntivirusDisabled in MDE telemetry
- Test 2Force MsMpEng Process Restart Sequence
Expected signal: System EventLog EventIDs 7036 (service state changed), 7034 (if crash simulated) for WinDefend service; multiple MsMpEng.exe process start events in DeviceProcessEvents
- Test 3Defender Configuration Tampering via Registry
Expected signal: Windows Defender Operational EventID 5007 (configuration changed); registry modification event in DeviceRegistryEvents for HKLM\SOFTWARE\Policies\Microsoft\Windows Defender
- Test 4Generate Windows Error Reporting Artifact for MsMpEng
Expected signal: Process access event against MsMpEng.exe in DeviceEvents (ActionType OpenProcess); file creation event for .dmp file; procdump.exe process creation with MsMpEng PID as argument
Unlock Pro Content
Get the full detection package for CVE-2026-45498 including response playbook, investigation guide, and atomic red team tests.