CVE-2021-42321
Microsoft Exchange Server Remote Code Execution Vulnerability
- Published
- Nov 10, 2021
- Updated
- Aug 19, 2026
- Assigning CNA
- microsoft
- Evidence observed
- Nov 17, 2021
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HHigh · next 30 days
- Percentile
- 99.8%
- Model date
- Oct 18, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
CISA Known Exploited
This CVE appears in the CISA Known Exploited Vulnerabilities catalog.
Summary
Microsoft Exchange Server Remote Code Execution Vulnerability
Sources
modules/exploits/windows/http/exchange_chainedserializationbinder_rce.rb
Metasploit Framework modulesDeclared conditions
- platform: Windows($.exploit_windows/http/exchange_chainedserializationbinder_rce.platform)
- verification: check_declared($.exploit_windows/http/exchange_chainedserializationbinder_rce.check)
- exch_CVE-2021-42321Exploit
Modified .NET deserialization payload for CVE-2021-42321, based on ysoserial.net, that writes files and bypasses Windows Defender to target Microsoft Exchange Server.
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