Microsoft Hyper-V RemoteFX vGPU Remote Code Execution Vulnerability
CVE-2020-1040 is a security vulnerability in Microsoft Hyper-V RemoteFX, added to CISA KEV on November 3, 2021. Patch priority: Patch this week.
What it is
Microsoft Hyper-V RemoteFX vGPU contains an improper input validation vulnerability due to the host server failing to properly validate input from an authenticated user on a guest operating system. Successful exploitation allows for remote code execution on the host operating system.
VulnCheck tracked exploitation 379 days before CISA's KEV listing. VulnCheck's broader catalog of in-the-wild exploitation evidence picked this up before it landed on CISA's formal list. Per-CVE fact about this entry; not a population claim about lead time in general.
Who's affected
Affects anyone running Microsoft Hyper-V RemoteFX. 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: 9.0 — CRITICAL
Weakness classification: CWE-20
Microsoft fix
No fixing KB is published yet in the Microsoft Security Update Guide for this CVE. Check Microsoft's advisory page directly if you need to verify whether an update has shipped.
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: 6.9% — higher than 93% 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.
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.