CVE-2021-26858: Microsoft Exchange Server Remote Code Execution Vulnerability

CISA Known Exploited Vulnerability (KEV)

Description

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Required action (CISA)

Apply updates per vendor instructions.

Notes

Reference CISA's ED 21-02 (https://www.cisa.gov/news-events/directives/ed-21-02-mitigate-microsoft-exchange-premises-product-vulnerabilities) for further guidance and requirements. Note: The due date for addressing this vulnerability aligns with the requirements outlined in ED 21-02. https://nvd.nist.gov/vuln/detail/CVE-2021-26858

Weakness behind it

CISA has not recorded a CWE for this entry, so the CVE → CWE → CAPEC → ATT&CK chain cannot be walked from here. That is a gap in the catalogue, not evidence the vulnerability has no weakness class — check the NVD record below.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26858
• KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog