Actively exploited · Published Nov 10, 2021 · Assigned by microsoft
CVE-2021-42321Microsoft Exchange Server Remote Code Execution Vulnerability
High 8.8 Exploited Ransomware
In plain English
A high-severity security flaw in Microsoft Exchange Server 2016 Cumulative Update 21 from Microsoft. Attackers are actively exploiting it in the wild (listed by CISA on November 17, 2021). It has been used in ransomware campaigns. The chance it is exploited in the next 30 days is estimated at 91.7% (higher than 99.8% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, public proof-of-concept code. Apply updates per vendor instructions.
Severity (CVSS 3.1)8.8High
Exploit odds (30 days)91.7%top 0.2% of all CVEs
Exploited in the wildYesCISA KEV since Nov 17, 2021
Attack tooling2Metasploit, Public PoC
CISA guidance
Apply updates per vendor instructions.
Federal agencies must remediate by Dec 1, 2021.
Official description
Microsoft Exchange Server Remote Code Execution Vulnerability
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 21 | 15.01.0 – before 15.01.2308.020 |
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 22 | 15.0.0 – before 15.01.2375.017 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 10 | 15.02.0 – before 15.02.0792.019 |
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 11 | 15.02.0 – before 15.02.0986.014 |
References
- Microsoft Exchange Server Remote Code Execution Vulnerability vendor-advisory, patch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42321 x_refsource_MISC, x_transferred
- http://packetstormsecurity.com/files/166153/Microsoft-Exchange-Server-Remote-Code-Execution.html x_refsource_MISC, x_transferred
- http://packetstormsecurity.com/files/168131/Microsoft-Exchange-Server-ChainedSerializationBinder-Remote-Code-Execution.html x_refsource_MISC, x_transferred
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42321 government-resource