CVE-2021-34473
Published: November 3, 2021
Official Description
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution.
CISA KEV Advisory
Microsoft Exchange Server Remote Code Execution Vulnerability
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution.
Apply updates per vendor instructions.
Risk Analysis
This unspecified vulnerability in Microsoft Exchange Server allows for remote code execution, meaning an attacker can run arbitrary commands on the server. The very high EPSS score of 0.94256 indicates a strong likelihood of exploitation, and its inclusion in the KEV confirms it is actively exploited.
This vulnerability is actively exploited in the wild, confirming that working exploits are available and being used by attackers. This flaw is remotely exploitable.
Apply all available security updates for Microsoft Exchange Server immediately. Ensure Exchange servers are properly patched and follow Microsoft's security best practices for hardening.
Technical Analysis
CVE-2021-34473 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-2021-34473 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-2021-34473 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