CVE-2026-45498: Microsoft Defender Denial of Service Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 20 May 2026, the same day the CVE record was published.
- How likely is exploitation in the next 30 days?
- 63.1%
EPSS score, percentile 99.2 of all scored records
- How severe?
- 4.0 Medium
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA deadline 3 Jun 2026. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- Which versions are affected?
Affected
- from 4.0.0.0 to before 4.18.26040.7
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
What to do
Required action, set by CISA
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA due date for this action: 3 June 2026.
Advisories and patches
Linked from CISA's catalog entry
- https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-45498
- https://nvd.nist.gov/vuln/detail/CVE-2026-45498
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 4.0.0.0 to before 4.18.26040.7 |
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
About this vulnerability
Microsoft Defender contains an unspecified vulnerability that allows for denial of service.
Summary: CISA's KEV catalog, as of 28 Oct 2026.
- CISA added CVE-2026-45498 to its Known Exploited Vulnerabilities (KEV) catalog on 20 May 2026.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 3 Jun 2026.
- The CVE record was published on 20 May 2026, the same day it was added to KEV.
- The CVE record carries a CVSS v3.1 base score of 4.0 (Medium), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 63.1% (percentile 99.2), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.
Description
Microsoft Defender Denial of Service Vulnerability
Microsoft Defender Denial of Service Vulnerability
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.
Weakness
- CWE-400: Uncontrolled Resource Consumption
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| 20 May 2026 | CVE record published |
| 20 May 2026 | Added to CISA KEV |
| 3 Jun 2026 | CISA due date for the required action |
| 10 Aug 2026 | CVE record last updated |
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