Microsoft Enhanced Cryptographic Provider Privilege Escalation Vulnerability
CVE-2021-31199 is a security vulnerability in Microsoft Enhanced Cryptographic Provider, added to CISA KEV on November 3, 2021. Patch order: fourth of four.
What is CVE-2021-31199?
Microsoft Enhanced Cryptographic Provider contains an unspecified vulnerability that allows for privilege escalation.
VulnCheck tracked exploitation 148 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 is affected by CVE-2021-31199?
Affects anyone running Microsoft Enhanced Cryptographic Provider. Microsoft products in a small practice typically sit close to credentials, email, or document workflows — treat the patch as in-scope.
What should I do about CVE-2021-31199?
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. Talk with us.
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: 5.2 — MEDIUM
Microsoft fix
- KB5003646 (Security Update)
- KB5003635 (Security Update)
- KB5003637 (Security Update)
- KB5003687 (Security Update)
- KB5003638 (Security Update)
- KB5003667 (Monthly Rollup)
- KB5003694 (Security Only)
- KB5003671 (Monthly Rollup)
- KB5003681 (Security Only)
- KB5003661 (Monthly Rollup)
- KB5003695 (Security Only)
- KB5003697 (Monthly Rollup)
- KB5003696 (Security Only)
Microsoft Exploitability Index (assessed at update release): Exploitation Detected
Microsoft has confirmed in-the-wild exploitation in the latest software release. This aligns with CISA's listing of this CVE.
Vendor workaround
No vendor workaround published. Patching is the only fix.
CISA due date
CISA's listed due date: November 17, 2021.
Federal civilian agencies work under CISA's Binding Operational Directive 26-04, which replaced BOD 22-01 on June 10, 2026. It sets the deadline for each affected system by:
- How exposed that system is to the internet
- Whether the attack can be automated
- How much control it gives an attacker
Its table gives catalogued vulnerabilities 3 or 14 days.
None of this binds a private business, but treat the date as a strong recommendation, especially if you handle regulated data (HIPAA, GLBA, ABA model rules).
EPSS
EPSS score: 3.0% — higher than 87% 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 Enhanced Cryptographic Provider entries
More CISA KEV entries for Microsoft Enhanced Cryptographic Provider. 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.