CVE-2021-26857

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.

Affected

• cpe microsoft/exchange server2010
• cpe microsoft/exchange server2013
• cpe microsoft/exchange server2016
• vendor Microsoft Exchange Serverversion unspecified

Sources

• CISA KEVCVE-2021-26857

  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-2021-26857

  Official CVE identifier

  cve.org
• FIRST EPSSCVE-2021-26857

  30-day exploitation probability 95.8%

  first.org
• NIST NVDCVE-2021-26857

  Microsoft Exchange Server Remote Code Execution Vulnerability

  nvd.nist.gov

References

• Patch · msrc.microsoft.com
• CISA note · nvd.nist.gov
• Patch · portal.msrc.microsoft.com
• US Government Resource · cisa.gov
• CISA note · cisa.gov