SolarWinds Serv-U FTP Server versions through 15.2.1 do not correctly sanitize and validate the user-supplied directory names, allowing malicious users to create directories that when clicked on (in the breadcrumb menu) will trigger cross site scripting payloads.
7b4d92cd96ecbdf9bbfd42665ba4d3b8Title: Stored XSS
Product: SolarWinds Serv-U FTP Server
Vendor Homepage: https://www.solarwinds.com/
Vulnerable Version: 15.2.1 and lower
Fixed Version: 15.2.2
CVE Number: CVE-2020-28001
Author: Jack Misiura from The Missing Link
Website: https://www.themissinglink.com.au
Timeline:
2020-10-30 Disclosed to Vendor
2021-01-21 Vendor releases patched version
2021-08-02 Publication
1. Vulnerability Description
SolarWinds Serv-U FTP server through 15.2.1 does not correctly sanitize and validate the user-supplied directory names, allowing malicious users to create directories that when clicked on (in the breadcrumb menu) will trigger XSS payloads.
2. PoC
On a vulnerable Serv-U FTP server installation, create a directory named as such:
%27%29%3Ba%3Dfunction%28b%29%20%7B%20alert%28%22XSS%22%29%3B%20%7D%3Ba%28%27
The payload contains ');a=function(b) { alert("XSS"); };a('
As soon as a user clicks on the directory name in the breadcrumb menu, it will trigger the stored XSS.
3. Solution
The vendor provides an updated version (15.2.2) which should be installed immediately.
4. Advisory URL
https://www.themissinglink.com.au/security-advisories
Jack Misiura
Application Security Consultant
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