CVE-2021-42321 on CISA KEV

Microsoft Exchange Server Remote Code Execution Vulnerability

01What CISA says about this vulnerability

Microsoft Exchange Server Remote Code Execution Vulnerability

02Required action — verbatim from CISA

Apply updates per vendor instructions.

03Notes & references

• portal.msrc.microsoft.com — https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-4232…
• packetstormsecurity.com — http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Cod…
• packetstormsecurity.com — http://packetstormsecurity.com/files/168131/Microsoft-Exchange-Server-ChainedSer…

04SARA's analyst layer — why this matters

This vulnerability is currently on the CISA KEV list, which CISA only adds CVEs to when there is reliable evidence of active exploitation in the wild. For federal civilian agencies, BOD 22-01 requires remediation by the due date above. For everyone else, KEV is the strongest "patch immediately" signal you can get from public threat intel.

05Affected products (summary)

Vendor	Product	Versions
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 21	15.01.0
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 10	15.02.0
Microsoft	Microsoft Exchange Server 2016 Cumulative Update 22	15.0.0
Microsoft	Microsoft Exchange Server 2019 Cumulative Update 11	15.02.0

06Detection

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