CVE-2021-36934 Microsoft Windows SAM Local Privilege Escalation Vulnerability
If a Volume Shadow Copy (VSS) shadow copy of the system drive is available, users can read the SAM file which would allow any user to escalate privileges to SYSTEM level.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 10 Feb 2022.
- Rated High severity (CVSS 7.8, scored by Vendor).
- Named in Cybergen threat actor reporting: APT29.
- It has been in the catalogue for 1,730 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
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 Versions
| Product | Versions |
|---|---|
| Microsoft Windows 10 Version 1809 | 10.0.17763.0 to before 10.0.17763.2114 |
| Microsoft Windows 10 Version 1809 | 10.0.0 to before 10.0.17763.2114 |
| Microsoft Windows 10 Version 1909 | 10.0.0 to before 10.0.18363.1734 |
| Microsoft Windows 10 Version 2004 | 10.0.0 to before 10.0.19041.1165 |
| Microsoft Windows 10 Version 20H2 | 10.0.0 to before 10.0.19042.1165 |
| Microsoft Windows 10 Version 21H1 | 10.0.0 to before 10.0.19043.1165 |
From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.
What To Do Now
- 1
Find it
Search your asset inventory and external attack surface for Microsoft Windows. Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management - 2
- 3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response - 4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
Vendor Advisories
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
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