CVE-2026-45498: Microsoft Defender Denial of Service Vulnerability
Microsoft Defender contains an unspecified vulnerability that allows for denial of service.
How it works
This weakness belongs to the denial-of-service class. An attacker can trigger conditions that render Microsoft Defender unavailable or unresponsive. The CISA summary provides no further technical detail on the trigger or affected component, so the precise abuse path must be confirmed against the vendor advisory.
Am I affected? How to find it in your systems
Microsoft Defender runs on Windows endpoints, servers, and some cloud-managed deployments. Inventory all systems running Microsoft Defender through standard endpoint management tools or Microsoft Defender for Endpoint consoles. Compare installed builds against the versions listed in the vendor advisory. Monitor security logs and service health telemetry for unexpected Defender process terminations or repeated restarts that could indicate attempted exploitation.
How to remediate
Apply mitigations per the vendor instructions referenced in the CISA advisory. Where Microsoft Defender is delivered as a cloud service, follow applicable BOD 22-01 guidance. If no effective mitigation is available, discontinue use of the affected product.
If you can't patch immediately
- Apply any vendor-supplied workarounds or configuration changes listed in the advisory.
- Segment systems running Microsoft Defender from untrusted networks to limit exposure.
- Enable additional monitoring for service availability and anomalous traffic patterns that could precede a denial-of-service attempt.
- Consider virtual patching or web application firewall rules only if they address the specific weakness class described by the vendor.
If your data may have been exposed
Actively exploited vulnerabilities lead to breaches. You can run a free exposure scan of your email to check known breach data.
AICompiled with AI assistance from public sources and published under our editorial standards.