CVE-2026-45498 | Microsoft Defender Denial of Service Vulnerability

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Microsoft Defender Denial of Service Vulnerability

Published: 2026-05-20 Last update: 2026-05-28 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-45498 is rated Active Exploitation (73/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 4.74%). CISA KEV confirms active exploitation (added 2026-05-20) affecting Microsoft / Defender. a weakness (CWE-400) Unauthenticated remote administrative access may be possible. The CISA remediation deadline has passed—treat as an emergency patch priority.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

CISA KEV Record for CVE-2026-45498

Name: Microsoft Defender Denial of Service Vulnerability · CISA KEV detail

Exploit added: 2026-05-20

Action due: 2026-06-03

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.

Exploit prediction scoring system (EPSS) score for CVE-2026-45498

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-07 4.11% 4.74% +0.64%
2 2026-05-26 3.21% 4.11% +0.90%
3 2026-05-25 — 3.21% —

Full EPSS history (6 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-45498

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
4.0 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:L)
Might cause slowdowns, glitches, or partial disruption—not a full brick.
 2.5 1.4 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-45498

GitHub Security Advisory for CVE-2026-45498

GHSA-8gp3-pghr-6wxp · Severity: medium — Microsoft Defender Denial of Service Vulnerability

Affected software / configurations for CVE-2026-45498

Vendor Product Version Raw CPE
microsoft defender_antimalware_platform < 4.18.26040.7 cpe:2.3:a:microsoft:defender_antimalware_platform:*:*:*:*:*:*:*:*

References for CVE-2026-45498

cvelogic Threat Intelligence