CVE-2021-36934: Microsoft Windows SAM Local Privilege Escalation Vulnerability
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.
Other sources
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.
— CISA
Windows Elevation of Privilege Vulnerability
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.19043.1165Patch KB5005033 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.19041.1165Patch KB5005033 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.18363.1734Patch KB5005031 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.19042.1165Patch KB5005033 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 10.0.17763.2114Patch KB5005030 - Configuration
After installing the referenced security update, manually delete all Volume Shadow Copy (VSS) shadow copies of system files, including the Security Accounts Manager (SAM) database, as specified by KB5005357 ("Delete Volume Shadow Copies").
Microsoft Windows Volume Shadow Copy Service (VSS) Delete all shadow copies of system files (including the SAM database) after applying the security update = Run deletion procedure referenced by KB5005357 - Operational
Ensure the VSS deletion mitigation is completed immediately after patch installation, because "Simply installing this security update will not fully mitigate this vulnerability" without manual shadow copy deletion (KB5005357).
Event History
Frequently Asked Questions
What is the severity of CVE-2021-36934?
CVE-2021-36934 has a critical severity rating due to its potential for privilege escalation.
How do I fix CVE-2021-36934?
To fix CVE-2021-36934, ensure that your Windows 10 system is updated to the latest security patch released by Microsoft.
What systems are affected by CVE-2021-36934?
CVE-2021-36934 affects multiple versions of Microsoft Windows 10, including versions 1809, 1909, 2004, 20H2, and 21H1.
What is the impact of exploiting CVE-2021-36934?
Exploiting CVE-2021-36934 allows an attacker to read the Security Account Manager (SAM) file, leading to elevation of privileges to SYSTEM level.
Is there a workaround for CVE-2021-36934 before applying a fix?
A recommended workaround for CVE-2021-36934 is to limit access to shadow copies and configure appropriate Access Control Lists (ACLs) until the patch is applied.