Zero-day vulnerability in SonicWall On-premise Email Security (ES)

Path traversal

The vulnerability was used in a chained attack to compromise the vulnerable systems.

Vulnerability details

Advisory: SB2021042016 - Path traversal in SonicWall Email Security

Vulnerable component: SonicWall On-premise Email Security (ES)

CVE-ID: CVE-2021-20023

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:N/A:N/E:H/RL:O/RC:C

CWE-ID: CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')


The vulnerability allows a remote user to perform directory traversal attacks.

The vulnerability exists due to input validation error when processing directory traversal sequences within the "branding"  feature. A remote authenticated user can send a specially crafted HTTP request and read arbitrary files on the system with NT AUTHORITY\SYSTEM account.

Request example:

https://<SonicWall ES host>/dload_apps?action=<any value>&path=..%2F..%2F..%2F..%2F..%2Fwindows%2Fsystem32%2Fcalc.exe&id=update

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