Zero-day vulnerability in Microsoft Exchange Server

Server-Side Request Forgery (SSRF)
CVE-2021-26855

Vulnerability details

Advisory: SB2021030301 - Multiple vulnerabilities in Microsoft Exchange Server

Vulnerable component: Microsoft Exchange Server

CVE-ID: CVE-2021-26855

CVSSv3 score: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-918 - Server-Side Request Forgery (SSRF)

Description:

The vulnerability allows a remote attacker to execute arbitrary code on the system.

The vulnerability exists due to insufficient validation of user-supplied input. A remote attacker can send specially crafted HTTP request to the Microsoft Exchange OWA interface, upload arbitrary file on the server and execute it.

Note, this vulnerability is being actively exploited in the wild.