Actively exploitedCVSS 4.0 · MEDIUM

CVE-2026-45498

Microsoft Defender contains an unspecified vulnerability that allows for denial of service.

Analysis

Microsoft Defender is currently being targeted by active exploits in the wild that allow for a Denial of Service. While the severity score is moderate, its presence on the CISA KEV catalog makes it a priority for anyone managing Windows-based development environments or production servers.

Relevant roles

WindowsCyberSecurityCloud

Severity

Score: 4.0(MEDIUM)

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

AV: LOCAL

AC: LOW

PR: NONE

UI: NONE

S: UNCHANGED

C: NONE

I: NONE

A: LOW

Weakness (CWE): NVD-CWE-noinfoCWE-400

CISA KEV

Added to KEV: 2026-05-20

Federal patch deadline: 2026-06-03

Known ransomware use: Unknown

Required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

EPSS

Probability of exploitation (next 30 days): 0.0372 (3.7%)

Percentile: 88.1%

EPSS: 2026-05-23

Affects

microsoft:defender_antimalware_platform

Technical description

Microsoft Defender Denial of Service Vulnerability

Published: 5/20/2026, 1:16:36 PM

Last modified: 5/20/2026, 7:05:46 PM

References

How to read this card

Actively exploited

KEV (Known Exploited Vulnerabilities) is CISA's catalog of CVEs confirmed as actively exploited in the real world. If a CVE is on KEV, someone is already using it in attacks.

CVSS 10.0

CVSS 10.0 — máxima severidad teórica. Explotable de forma remota, sin privilegios, con impacto total. Aún no confirmada como explotada en el mundo real, pero parchea ya.

AI-recommended

Un modelo de lenguaje revisó el CVE y consideró que afecta a software ampliamente desplegado o herramientas comunes de desarrollo. Un humano del equipo aprobó la publicación antes de que llegara aquí.

Categorías de impacto que evalúa la IA

widely_deployed_infra — kernel Linux, OpenSSL, glibc, k8s, Docker, nginx, OpenSSH.

popular_dev_tooling — Node.js, Python, Go, React, Next.js, librerías comunes de npm/pip.

common_consumer_software — Chrome, Firefox, Windows, macOS, apps móviles populares.

enterprise_saas — GitHub, GitLab, Atlassian, Salesforce, Cisco, Fortinet, Ivanti.

niche_software — CMS regionales, herramientas de hobby, librerías de poco uso.

not_relevant — firmware específico de proveedor, software descontinuado.

EPSS — EPSS (Exploit Prediction Scoring System) by FIRST.org estimates the probability that a CVE will be exploited in the next 30 days. Range is 0 to 1; very fresh CVEs typically score low until evidence accumulates.