CVE-2021-27065: Microsoft Exchange Server Remote Code Execution Vulnerability

Vulnerability summary

CVE-2021-27065 is a high (CVSS 7.8) Path Traversal vulnerability in Microsoft Exchange Server. It is known to be exploited: CISA lists it, first on 03-11-2021. It has been used in ransomware campaigns. EPSS estimates a 99.88% chance of exploitation in the next 30 days, higher than 99.9% of scored vulnerabilities. 4 public exploits are recorded.

Timeline

1. 02-03-2021
   PublishedVulnerability first disclosed.
2. 03-11-2021
   Added to CISA KEVMicrosoft Exchange Server Remote Code Execution Vulnerability
3. 03-05-2022
   CISA remediation dueApply updates per vendor instructions.
4. 01-10-2026
   Last modifiedVulnerability information updated.

Description

Microsoft Exchange Server Remote Code Execution Vulnerability

• CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.