CVE-2021-26855 Microsoft Exchange Server Remote Code Execution
Attackers can exploit a Server-Side Request Forg flaw in Microsoft Exchange Server to achieve remote code execution.
- Exploited in the wild
- Since 3 Nov 2021
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-26855?
CVE-2021-26855 is a critical server-side request forgery vulnerability in Microsoft Exchange Server, published on 2 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Microsoft Exchange Server Remote Code Execution Vulnerability
Weakness: CWE-918
Which versions are affected by CVE-2021-26855?
It affects 1 product.
Products include Microsoft Exchange Server.
How do I fix CVE-2021-26855?
No fix has been published for CVE-2021-26855 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 May 2022.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2021-26855 being exploited?
Yes. Attackers have exploited CVE-2021-26855 in the wild since at least 3 Nov 2021, including in ransomware campaigns.
Public exploit code: 3 Metasploit modules, 4 Exploit-DB entries, 1 Nuclei template and 53 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-2021-34523 Microsoft Exchange Server Privilege Escalation
- CVE-2023-21529 Microsoft Exchange Server Deserialization of Untrusted Data
- CVE-2022-41080 Microsoft Exchange Server Privilege Escalation
Sources
Also known as GHSA-6784-2mh5-cq56.