What’s Vulnerable › Vulnerabilities

CVE-2021-36934: Windows Elevation of Privilege Vulnerability

• Severity: medium (CVSS 4.6 v2.0)
• Exploited in the wild: yes — in CISA KEV since 2022-02-10
• EPSS: 67.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-07-22 · updated 2026-08-10

Description

An elevation of privilege vulnerability exists because of overly permissive Access Control Lists (ACLs) on multiple system files, including the Security Accounts Manager (SAM) database. An attacker who successfully exploited this vulnerability could run arbitrary code with SYSTEM privileges. An attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. An attacker must have the ability to execute code on a victim system to exploit this vulnerability. After installing this security update, you must manually delete all shadow copies of system files, including the SAM database, to fully mitigate this vulnerabilty. Simply installing this security update will not fully mitigate this vulnerability. See KB5005357- Delete Volume Shadow Copies.

Affected products

• Microsoft Windows 10: before 10.0.17763.2114 — fixed in 10.0.17763.2114
• Microsoft Windows 10 1909: before 10.0.18363.1734 — fixed in 10.0.18363.1734
• Microsoft Windows 10 2004: before 10.0.19041.1165 — fixed in 10.0.19041.1165
• Microsoft Windows 10 20H2: before 10.0.19042.1165 — fixed in 10.0.19042.1165
• Microsoft Windows 10 21H1: before 10.0.19043.1165 — fixed in 10.0.19043.1165
• Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.2114 — fixed in 10.0.17763.2114
• Microsoft Windows 10 1909: from 10.0.0 before 10.0.18363.1734 — fixed in 10.0.18363.1734
• Microsoft Windows 10 2004: from 10.0.0 before 10.0.19041.1165 — fixed in 10.0.19041.1165
• Microsoft Windows 10 20H2: from 10.0.0 before 10.0.19042.1165 — fixed in 10.0.19042.1165
• Microsoft Windows 10 21H1: from 10.0.0 before 10.0.19043.1165 — fixed in 10.0.19043.1165

How to fix

Upgrade to a fixed version: Microsoft Windows 10 10.0.17763.2114; Microsoft Windows 10 1909 10.0.18363.1734; Microsoft Windows 10 2004 10.0.19041.1165; Microsoft Windows 10 20H2 10.0.19042.1165; Microsoft Windows 10 21H1 10.0.19043.1165; Microsoft Windows 10 10.0.17763.2114; Microsoft Windows 10 1909 10.0.18363.1734; Microsoft Windows 10 2004 10.0.19041.1165; Microsoft Windows 10 20H2 10.0.19042.1165; Microsoft Windows 10 21H1 10.0.19043.1165. Check the vendor advisory for mitigations.

References

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-36934
• http://packetstormsecurity.com/files/164006/HiveNightmare-AKA-SeriousSAM.html
• https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-36934
• https://www.kb.cert.org/vuls/id/506989
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-36934

Get alerted when CVE-2021-36934 or the next vulnerability affects your stack