CVE-2021-33771
Published: November 3, 2021
Official Description
Microsoft Windows kernel contains an unspecified vulnerability that allows for privilege escalation.
CISA KEV Advisory
Microsoft Windows Kernel Privilege Escalation Vulnerability
Microsoft Windows kernel contains an unspecified vulnerability that allows for privilege escalation.
Apply updates per vendor instructions.
Risk Analysis
This is an unspecified vulnerability in the Microsoft Windows kernel that allows for privilege escalation. Its inclusion in CISA's KEV catalog and active exploitation in the wild make it a critical concern, despite the lack of specific CVSS scores. The high EPSS score further emphasizes the urgency.
This vulnerability is actively being exploited in the wild and is listed in CISA's Known Exploited Vulnerabilities catalog. The nature of the flaw allows for privilege escalation.
Apply all available security updates and patches for Microsoft Windows to address this privilege escalation vulnerability. Ensure systems are kept up-to-date to prevent exploitation.
Technical Analysis
CVE-2021-33771 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2021-33771 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Affected Vendors & Products
Exploit & PoC Resources
All References (1)
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-33771 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1