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Findings

CVE-2021-26855

Microsoft Exchange Server Remote Code Execution Vulnerability

Published Mar 2, 2021 · updated Aug 19, 2026 · microsoft exchange server

Microsoft Exchange Server Remote Code Execution Vulnerability

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. 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.

  2. Nov 3, 2021 · CISA KEV

    Known exploited

    Apply updates per vendor instructions.

  3. May 3, 2022 · CISA KEV

    Remediation due

    Apply updates per vendor instructions.

  4. 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 KEVConfirmed exploitationCVE-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.orgVulnerability recordCVE-2021-26855

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-26855

    30-day exploitation probability 100.0%

    first.org
  • Exploit DatabasePublic exploit reference49637

    Public archive entry. The exploit body is not stored here.

    exploit-db.com
  • Exploit DatabasePublic exploit reference49663

    Public archive entry. The exploit body is not stored here.

    exploit-db.com
  • Exploit DatabasePublic exploit reference49879

    Public archive entry. The exploit body is not stored here.

    exploit-db.com
  • Metasploit ModulesPublic exploit moduleauxiliary_gather/exchange_proxylogon_collector

    Public module reference (normal). Module source is not copied into this catalog.

    rapid7.com
  • Metasploit ModulesPublic exploit moduleauxiliary_scanner/http/exchange_proxylogon

    Public module reference (normal). Module source is not copied into this catalog.

    rapid7.com
  • Metasploit ModulesPublic exploit moduleexploit_windows/http/exchange_proxylogon_rce

    Public module reference (excellent). Module source is not copied into this catalog.

    rapid7.com
  • NIST NVDVulnerability recordCVE-2021-26855

    Microsoft Exchange Server Remote Code Execution Vulnerability

    nvd.nist.gov
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com
  • Packet Storm SecurityCited referencehttp://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html

    Packet Storm link already published on the finding.

    packetstormsecurity.com

References