Impact
The Cross-Origin-Resource-Sharing policy in Open Zaak is currently wide open - every client is allowed.
This allows evil.com to run scripts that perform AJAX calls to known Open Zaak installations, and the browser will not block these. This was intended to only apply to development machines running on localhost/127.0.0.1.
Patches
Open Zaak 1.3.3 disables CORS by default, while it can be opted-in through environment variables.
Workarounds
The vulnerability does not actually seem exploitable because:
- The session cookie has a
Same-Site: Lax policy which prevents it from being sent along in Cross-Origin requests
- All pages that give access to (production) data are login-protected
Access-Control-Allow-Credentials is set to false
- CSRF checks probably block the remote origin, since they're not explicitly added to the trusted allowlist.
References
For more information
If you have any questions or comments about this advisory:
Impact
The Cross-Origin-Resource-Sharing policy in Open Zaak is currently wide open - every client is allowed.
This allows evil.com to run scripts that perform AJAX calls to known Open Zaak installations, and the browser will not block these. This was intended to only apply to development machines running on localhost/127.0.0.1.
Patches
Open Zaak 1.3.3 disables CORS by default, while it can be opted-in through environment variables.
Workarounds
The vulnerability does not actually seem exploitable because:
Same-Site: Laxpolicy which prevents it from being sent along in Cross-Origin requestsAccess-Control-Allow-Credentialsis set tofalseReferences
For more information
If you have any questions or comments about this advisory: