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[ CVE-2021-36934 · Published 22 Jul 2021 ]

Microsoft Windows SAM Local Privilege Escalation Vulnerability

Exploited · CISA KEV CVSS 7.8 EPSS 67%Fix available

[ Why it matters ]Priority signals

  • Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2022-02-10
  • EPSS: 67% chance of exploitation in the next 30 days (higher than 99% of CVEs)

[ Description ]Official 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.

CISA: 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.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 24 Feb 2022): Apply updates per vendor instructions.

[ References ]References