CVE-2026-45498
Microsoft Defender Denial of Service Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 3 June 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
Description
Microsoft Defender Denial of Service Vulnerability
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 63.08% probability · 99th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 20 May 2026 · due 3 June 2026
- Weakness
- CWE-400
- Affected
- microsoft/defender antimalware platform
- Source
- secure@microsoft.com
EPSS moved from 1.3% on 24 September 2026 to 63.1% on 27 October 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
CISA notes
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-45498 ; https://nvd.nist.gov/vuln/detail/CVE-2026-45498
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45498Vendor Advisory
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-45498Third Party Advisory, US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.