CVE-2021-26855
Microsoft Exchange Server Remote Code Execution Vulnerability
Published Mar 2, 2021 · updated Aug 19, 2026 · microsoft exchange server
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
Timeline
Detection, updates, and resolution for this record.
Mar 2, 2021 · Catalog
Detected
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
Nov 3, 2021 · CISA KEV
Known exploited
Apply updates per vendor instructions.
May 3, 2022 · CISA KEV
Remediation due
Apply updates per vendor instructions.
Aug 19, 2026 · Catalog
Updated
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
Required action
Apply updates per vendor instructions.
CISA due date May 3, 2022
Affected
- cpe microsoft/exchange server2013
- cpe microsoft/exchange server2016
- vendor Microsoft Exchange Serverversion unspecified
Sources
- CISA KEVCVE-2021-26855
Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.
cisa.gov - CVE.orgCVE-2021-26855
Official CVE identifier
cve.org - FIRST EPSSCVE-2021-26855
30-day exploitation probability 100.0%
first.org - Exploit Database49637
Public archive entry. The exploit body is not stored here.
exploit-db.com - Exploit Database49663
Public archive entry. The exploit body is not stored here.
exploit-db.com - Exploit Database49879
Public archive entry. The exploit body is not stored here.
exploit-db.com - Metasploit Modulesauxiliary_gather/exchange_proxylogon_collector
Public module reference (normal). Module source is not copied into this catalog.
rapid7.com - Metasploit Modulesauxiliary_scanner/http/exchange_proxylogon
Public module reference (normal). Module source is not copied into this catalog.
rapid7.com - Metasploit Modulesexploit_windows/http/exchange_proxylogon_rce
Public module reference (excellent). Module source is not copied into this catalog.
rapid7.com - NIST NVDCVE-2021-26855
Microsoft Exchange Server Remote Code Execution Vulnerability
nvd.nist.gov - Packet Storm Securityhttp://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html
Packet Storm link already published on the finding.
packetstormsecurity.com - Packet Storm Securityhttp://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html
Packet Storm link already published on the finding.
packetstormsecurity.com - Packet Storm Securityhttp://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html
Packet Storm link already published on the finding.
packetstormsecurity.com - Packet Storm Securityhttp://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html
Packet Storm link already published on the finding.
packetstormsecurity.com