CVE-2021-1679: Windows CryptoAPI Denial of Service Vulnerability

CVE-2021-1679 is a denial of service vulnerability in Windows CryptoAPI, rated Important by Microsoft, with a CVSS 3.1 base score of 6.5 (Medium). An attacker can exploit it remotely over the network, without any privileges and only if a user takes an action. Microsoft has not reported exploitation in the wild and rates exploitation as less likely. The EPSS model estimates a 3.74% probability of exploitation activity in the next 30 days, higher than 90% of all scored vulnerabilities. Microsoft released the fix on 12 January 2021 in the January 2021 Patch Tuesday, delivered through 14 security updates (KB4598242, KB4598245, KB4598230, KB4598229 and more). It affects 40 products in 2 product families (Windows, ESU).

Key facts

CVE ID

CVE-2021-1679

Severity

Medium CVSS 6.5

Microsoft severity

Important

Impact

Denial of Service

Exploited in the wild

No

Publicly disclosed

No

Exploitation likelihood

Less Likely

EPSS

3.74% (percentile 90%)

CISA KEV

Not listed

Released

12 January 2021

Last updated

12 January 2021

Patch Tuesday

January 2021 Patch Tuesday

Product families

Windows, ESU

CVSS score and vector

Microsoft scores CVE-2021-1679 at 6.5 (temporal 5.7) using CVSS 3.1. Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C

Affected products (40)

Windows

ESU

Security updates (14)

• KB4598242 (Security Update)
• KB4598245 (Security Update)
• KB4598230 (Security Update)
• KB4598229 (Security Update)
• KB4598231 (Security Update)
• KB4598243 (Security Update)
• KB4598279 (Monthly Rollup)
• KB4598289 (Security Only)
• KB4598285 (Monthly Rollup)
• KB4598275 (Security Only)
• KB4598288 (Monthly Rollup)
• KB4598287 (Security Only)
• KB4598278 (Monthly Rollup)
• KB4598297 (Security Only)

NIST NVD data

NVD status

Modified

NVD CVSS

6.5 (MEDIUM)

Published to NVD

12 January 2021

NVD last modified

17 June 2026

Affected configurations (CPE)

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-1679
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1679

Revision history

Related vulnerabilities

Other Windows CryptoAPI vulnerabilities

• CVE-2023-35339: Windows CryptoAPI Denial of Service Vulnerability (High, CVSS 7.5, July 2023)
• CVE-2023-24938: Windows CryptoAPI Denial of Service Vulnerability (Medium, CVSS 6.5, June 2023)
• CVE-2023-24937: Windows CryptoAPI Denial of Service Vulnerability (Medium, CVSS 6.5, June 2023)
• CVE-2022-34689: Windows CryptoAPI Spoofing Vulnerability (High, CVSS 7.5, October 2022)
• CVE-2020-0601: Windows CryptoAPI Spoofing Vulnerability (High, CVSS 8.1, January 2020)

More from the January 2021 Patch Tuesday

• CVE-2021-1648: Microsoft splwow64 Elevation of Privilege Vulnerability (High, CVSS 7.8)
• CVE-2021-1709: Windows Win32k Elevation of Privilege Vulnerability (High, CVSS 7)
• CVE-2021-1636: Microsoft SQL Elevation of Privilege Vulnerability (High, CVSS 8.8)
• CVE-2021-1658: Remote Procedure Call Runtime Remote Code Execution Vulnerability (High, CVSS 8.8)
• CVE-2021-1660: Remote Procedure Call Runtime Remote Code Execution Vulnerability (High, CVSS 8.8)
• CVE-2021-1664: Remote Procedure Call Runtime Remote Code Execution Vulnerability (High, CVSS 8.8)
• CVE-2021-1666: Remote Procedure Call Runtime Remote Code Execution Vulnerability (High, CVSS 8.8)
• CVE-2021-1667: Remote Procedure Call Runtime Remote Code Execution Vulnerability (High, CVSS 8.8)
• CVE-2021-1669: Windows Remote Desktop Security Feature Bypass Vulnerability (High, CVSS 8.8)
• CVE-2021-1671: Remote Procedure Call Runtime Remote Code Execution Vulnerability (High, CVSS 8.8)
• CVE-2021-1673: Remote Procedure Call Runtime Remote Code Execution Vulnerability (High, CVSS 8.8)
• CVE-2021-1674: Windows Remote Desktop Protocol Core Security Feature Bypass Vulnerability (High, CVSS 8.8)

All vulnerabilities of this release: January 2021 Patch Tuesday

Sources

• Microsoft Security Update Guide: CVE-2021-1679
• NIST NVD: CVE-2021-1679
• CVE.org record: CVE-2021-1679