CVE-2021-42321 Microsoft Exchange Server Remote Code Execution
Attackers can execute arbitrary code on Microsoft Exchange Server, requiring immediate patching by administrators.
- Exploited in the wild
- Since 17 Nov 2021
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-42321?
CVE-2021-42321 is a high-severity code injection vulnerability in Microsoft Exchange Server, published on 10 Nov 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Microsoft Exchange Server Remote Code Execution Vulnerability
Which versions are affected by CVE-2021-42321?
It affects 1 product.
Products include Microsoft Exchange Server.
How do I fix CVE-2021-42321?
No fix has been published for CVE-2021-42321 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 1 Dec 2021.
Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.
Is CVE-2021-42321 being exploited?
Yes. Attackers have exploited CVE-2021-42321 in the wild since at least 17 Nov 2021, including in ransomware campaigns.
Public exploit code: 1 Metasploit module and 3 proofs of concept on GitHub.
Other vulnerabilities in Microsoft Exchange Server
- CVE-2024-21410 Microsoft Exchange Server Privilege Escalation
- CVE-2021-34473 Microsoft Exchange Server Remote Code Execution
- CVE-2021-26855 Microsoft Exchange Server Remote Code Execution
- CVE-2021-34523 Microsoft Exchange Server Privilege Escalation
- CVE-2023-21529 Microsoft Exchange Server Deserialization of Untrusted Data
Sources
Also known as GHSA-3f87-66x4-f3p7.