Microsoft .NET Framework Remote Code Execution Vulnerability
CVE-2020-0646 is a security vulnerability in Microsoft .NET Framework, added to CISA KEV on November 3, 2021. Patch priority: Patch this week.
What it is
Microsoft .NET Framework contains an improper input validation vulnerability that allows for remote code execution.
Who's affected
Affects anyone running Microsoft .NET Framework. Microsoft products in a small practice typically sit close to credentials, email, or document workflows — treat the patch as in-scope.
What to do
Apply updates per vendor instructions.
If you don't have someone in-house to verify the patch deployed across every endpoint — or you're not sure whether you're affected — that's exactly the kind of triage we do. Book a free 20-minute triage call.
Insurance readiness
Your insurer will ask if this is patched.
Unpatched entries on CISA's Known Exploited Vulnerabilities list are exactly what cyber-insurance carrier questionnaires probe for, and knowing which controls they check is how you keep a renewal from stalling.
Get the free carrier questionnaire →Severity
CVSS base score: 9.8 — CRITICAL
Weakness classification: CWE-91
Microsoft fix
- KB4535102 (Monthly Rollup)
- KB4534976 (Security Only)
- KB4535104 (Monthly Rollup)
- KB4534978 (Security Only)
- KB4535103 (Monthly Rollup)
- KB4534977 (Security Only)
- KB4534271 (Security Update)
- KB4532936 (Security Update)
- KB4532935 (Security Update)
- KB4532933 (Security Update)
- KB4535101 (Security Update)
- KB4532938 (Security Update)
- KB4535105 (Monthly Rollup)
- KB4534979 (Security Only)
- KB4534293 (Security Update)
- KB4534306 (Security Update)
- KB4534276 (Security Update)
Microsoft Exploitability Index (assessed at update release): Exploitation Less Likely
This CVE is on CISA's Known Exploited Vulnerabilities catalog. Microsoft's index reflects their release-time forecast, not current observed activity, and is not automatically revised upward when exploitation appears later.
Vendor workaround
No vendor workaround published. Patching is the only fix.
CISA due date
Federal deadline: May 3, 2022. Federal agencies must complete the required action by this date. For private SMBs the deadline is advisory — but treat it as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 99.2% — higher than 100% of all scored CVEs.
EPSS estimates the probability of exploitation activity in the next 30 days. Every entry on this site is already confirmed exploited, so read it as relative urgency among the things you still have open, not as permission to wait.
Other exploited Microsoft .NET Framework entries
More CISA KEV entries for Microsoft .NET Framework. Same product line, same actively-exploited status.
Source
This entry comes from CISA's Known Exploited Vulnerabilities catalog, public US-Government data we pull daily. The plain-language framing and the what-to-do guidance above are ours. View the original entry on cisa.gov.