Title: Path traversal
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-2020-27994
Author: Jack Misiura from The Missing Link
Website: https://www.themissinglink.com.au
Timeline:
2020-10-28 Disclosed to Vendor
2021-01-21 Vendor releases patched version
2021-08-02 Publication
1. Vulnerability Description
SolarWinds Serv-U File Server through 15.2.1 does not correctly validate path information, allowing the disclosure of files and directories outside of the user's home directory via a specially crafted GET request.
2. PoC
On a vulnerable Serv-U installation issue the following GET request to get a listing of files and directories above the user's directory:
https://<serv-u host>/Web Client/?Command=List&dir=\..\*.*
The user *MUST* be locked to their directory, and only access granted must be the said directory. Directory listing must be enabled. If any of the above is not present, the exploit will not work.
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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