VulnerabilityAnalyzed
CVE-2021-34473
Microsoft Exchange Server Remote Code Execution Vulnerability
KEVCRITICAL 9.1EPSS 100.0%
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 17 November 2021). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
Description
Microsoft Exchange Server Remote Code Execution Vulnerability
- CVSS 3.1
- 9.1 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
- EPSS
- 100.00% probability · 100th percentile
- CISA KEV
- Listed 3 November 2021 · due 17 November 2021 · used in ransomware campaigns
- Weakness
- CWE-918
- Affected
- microsoft/exchange server
- Source
- secure@microsoft.com
CISA notes
Apply updates per vendor instructions. https://nvd.nist.gov/vuln/detail/CVE-2021-34473
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-34473Patch, Vendor Advisory
- http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.htmlExploit, Third Party Advisory, VDB Entry
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-34473Patch, Vendor Advisory
- https://www.zerodayinitiative.com/advisories/ZDI-21-821/Third Party Advisory, VDB Entry
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-34473US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.