CVE-2021-31978
Microsoft Defender Denial of Service Vulnerability
5.5 Medium
Microsoft Defender Denial of Service Vulnerability
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
1.23%Up 0.7 points since Jun 9, 2021
What each source reports
CVE List Score used
Microsoft Defender Denial of Service Vulnerability
Microsoft Defender Denial of Service Vulnerability
- Record
CVE-2021-31978- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C - Updated
- 2026-11-02
EUVDEUVD-2021-18850
Microsoft Defender Denial of Service Vulnerability
- Record
EUVD-2021-18850- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-9mqr-qv46-7v82
Microsoft Defender Denial of Service Vulnerability
Microsoft Defender Denial of Service Vulnerability
- Record
GHSA-9mqr-qv46-7v82- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
NVD
Microsoft Defender Denial of Service Vulnerability
- Record
CVE-2021-31978- CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - CVSS 3.1
- 5.5 Medium
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 2.1 Low
AV:L/AC:L/Au:N/C:N/I:N/A:P - Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-31978 is a medium vulnerability (CVSS 5.5) in Microsoft Malware Protection Engine, published June 8, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.23%, the 68th percentile. No source names a fixed version.