CVE-2026-45498: medium-severity vulnerability in Microsoft Defender Antimalware Platform
Microsoft Defender Denial of Service Vulnerability
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
Prioritize patching. It under exploitation confirmed by CISA and has an official Brazilian government alert.
Brazil's federal government published an alert, recommendation or bulletin that cites this vulnerability.
- CISC Gov.br · 29 May 2026Seis Vulnerabilidades Zero-Day no Microsoft Windowsread on gov.br ↗
- CTIR Gov · ALERTA 43/2026 · 25 May 2026Vulnerabilidade crítica no Defenderread on gov.br ↗
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Microsoft Defender can be made to stop working properly when it processes specially crafted files, leaving your computer unprotected. An attacker can exploit this to disable your antivirus temporarily.
A resource exhaustion vulnerability (CWE-400) in Microsoft Defender's file processing engine allows an unauthenticated local attacker to trigger excessive resource consumption through maliciously crafted input files, resulting in denial of service. The attack vector is local file processing, requiring no elevated privileges but direct interaction with the affected component.
The full analysis of this CVE is available in Portuguese →
In the same product, most dangerous first.