CVE-2021-31201
CVE-2021-31201 is a security flaw in Microsoft Enhanced Cryptographic Provider. Someone who already has a foothold can use Microsoft Enhanced Cryptographic Provider to take full control of the machine. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 3 Nov 2021.[1]
Microsoft Enhanced Cryptographic Provider is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Fixed in version 10.0.17763.1999, 10.0.18363.1621, 10.0.19043.1052 and 10.0.19041.1052 and others.
Description
CISA calls it a privilege escalation in Microsoft Enhanced Cryptographic Provider. In its words: “Microsoft Enhanced Cryptographic Provider contains an unspecified vulnerability that allows for privilege escalation.”[1]
It scores 5.2 out of 10 on the Common Vulnerability Scoring System, which rates it medium, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record lists these fixed versions: in each line, everything before the version shown is affected.[2]
| Product | Fixed in |
|---|---|
| Windows 10 Version 1809 | 10.0.17763.1999 |
| Windows Server 2019 | 10.0.17763.1999 |
| Windows Server 2019 (Server Core installation) | 10.0.17763.1999 |
| Windows 10 Version 1909 | 10.0.18363.1621 |
| Windows 10 Version 21H1 | 10.0.19043.1052 |
| Windows 10 Version 2004 | 10.0.19041.1052 |
| Windows Server version 2004 | 10.0.19041.1052 |
| Windows 10 Version 20H2 | 10.0.19042.1052 |
Most families won’t have Microsoft Enhanced Cryptographic Provider; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 3 Nov 2021, 148 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 17 Nov 2021 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 3%. That’s in the top 15% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Microsoft has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Microsoft Enhanced Cryptographic Provider is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed (fixed in version 10.0.17763.1999, 10.0.18363.1621, 10.0.19043.1052 and 10.0.19041.1052 and others), or not in use. CISA gave US government agencies until 17 Nov 2021 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 5.2.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 3%.[4] |
See also
Other Microsoft Enhanced Cryptographic Provider flaws
- CVE-2021-31199: privilege escalation ·
Other Microsoft flaws
- CVE-2026-96951, Microsoft Windows: command injection ·
- CVE-2026-65660, Microsoft SharePoint: code injection ·
- CVE-2026-85880, Microsoft Windows: heap-based buffer overflow ·
- CVE-2026-81963, Microsoft Windows: link following ·
- CVE-2019-1068, Microsoft SQL Server: remote code execution ·
Similar flaws
- CVE-2026-111357, Ivanti Connect Secure: missing authentication for critical function ·
- CVE-2026-97229, GitLab Community Edition and Enterprise Edition: integer overflow or wraparound ·
- CVE-2026-76418, Cisco Secure Firewall ASA Software and Cisco Secure FTD Software: unchecked return value to NULL pointer dereference ·
- CVE-2026-48356, Adobe Commerce and Magento: unrestricted upload of file with dangerous type ·
- CVE-2026-111497, Google Brotli: unchecked return value ·
Added the same day
- CVE-2021-42258, BQE BillQuick Web Suite: SQL injection ·
- CVE-2021-42013, Apache HTTP Server: path traversal ·
- CVE-2021-41773, Apache HTTP Server: path traversal ·
- CVE-2021-40539, Zoho ManageEngine: aDSelfService plus authentication bypass ·
- CVE-2021-40444, Microsoft MSHTML: remote code execution ·
Every Microsoft flaw on CISA’s list · Everything added in November 2021
References
- ^ Cybersecurity and Infrastructure Security Agency. “Microsoft Enhanced Cryptographic Provider Privilege Escalation Vulnerability”. Known Exploited Vulnerabilities Catalog, added 3 Nov 2021.
- ^ National Institute of Standards and Technology. “CVE-2021-31201 Detail”. National Vulnerability Database, published 8 Jun 2021.
- ^ Microsoft. Advisories and fixes: portal.msrc.microsoft.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.026, percentile 85.4, 31 Oct 2026.
- CVE Program. “CVE-2021-31201”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.