CVE-2020-26251

Open Zaak is a modern, open-source data- and services-layer to enable zaakgericht werken, a Dutch approach to case management. In Open Zaak before version 1.3.3 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. Open Zaak 1.3.3 disables CORS by default, while it can be opted-in through environment variables. The vulnerability does not actually seem exploitable because: a) The session cookie has a `Same-Site: Lax` policy which prevents it from being sent along in Cross-Origin requests. b) All pages that give access to (production) data are login-protected c) `Access-Control-Allow-Credentials` is set to `false` d) CSRF checks probably block the remote origin, since they're not explicitly added to the trusted allowlist.

• CWE-346
• CWE-346

• https://github.com/open-zaak/open-zaak/blob/master/CHANGELOG.rst#133-2020-12-17Release Notes, Third Party Advisory
• https://github.com/open-zaak/open-zaak/commit/952269269f1b629fce9c94485f83ac13f31d6c46Patch, Third Party Advisory
• https://github.com/open-zaak/open-zaak/security/advisories/GHSA-chhr-gxrg-64x7Third Party Advisory
• https://github.com/open-zaak/open-zaak/blob/master/CHANGELOG.rst#133-2020-12-17Release Notes, Third Party Advisory
• https://github.com/open-zaak/open-zaak/commit/952269269f1b629fce9c94485f83ac13f31d6c46Patch, Third Party Advisory
• https://github.com/open-zaak/open-zaak/security/advisories/GHSA-chhr-gxrg-64x7Third Party Advisory

Published

Dec 18, 2020

Last Modified

Jun 17, 2026

Status

Modified