Detect Microsoft Defender Denial of Service Vulnerability (CVE-2026-45498) in Elastic Security
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
Elastic Detection Query
sequence by host.name with maxspan=1h
[process where event.action == "start" and process.name : "MsMpEng.exe"] by host.name
[process where event.action == "stop" and process.name : "MsMpEng.exe"] by host.name
[process where event.action == "start" and process.name : "MsMpEng.exe"] by host.name
| head 100
/* Alternative: service crash and restart pattern */
/*
any where
(
(event.provider == "Microsoft-Windows-Windows Defender" and event.code in ("5001", "5007", "5010", "5012", "2004"))
or
(event.provider == "Service Control Manager" and event.code in ("7034", "7031") and message : "*Defender*")
)
and not user.name : ("SYSTEM", "NT AUTHORITY\\SYSTEM")
*/EQL sequence detection for Microsoft Defender process stop/start cycles indicating potential DoS exploitation of CVE-2026-45498. Detects rapid restart sequences of the MsMpEng.exe process within a 1-hour window.
Data Sources
Required Tables
False Positives & Tuning
- Windows Update or patch cycles that legitimately restart Defender
- Elastic Defend or third-party EDR conflicts causing Defender restarts
- System hibernation or sleep cycles triggering process restart events
- Administrative scripts performing Defender service maintenance
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
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