CVE-2021-26857: 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-2021-26857

Weakness behind it

CISA records this vulnerability as an instance of CWE-502. From there the chain continues into CAPEC attack patterns and ATT&CK techniques, all inside this corpus.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26857
• KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog