CVE-2021-43807

Opencast versions prior to 9.10 allow HTTP method spoofing, allowing to change the assumed HTTP method via URL parameter. This allows attackers to turn HTTP GET requests into PUT requests or an HTTP form to send DELETE requests. This bypasses restrictions otherwise put on these types of requests and aids in cross-site request forgery (CSRF) attacks, which would otherwise not be possible.

Workarounds

You can mitigate the problem by setting the SameSite=Strict attribute for your cookies. If this is a viable option for you depends on your integrations. We strongly recommend updating in any case.

References

• Fix for 10.0
• Fix for 9.10

For more information

If you have any questions or comments about this advisory:

• Open an issue in our issue tracker
• Email us at [email protected]

The vulnerability allows attackers to craft links or forms which may change the server state. For example, the following GET request would create a new user:

% curl -i -u admin:opencast \
  'https://legacy.opencast.org/admin-ng/users/test.json?_method=PUT&username=test&password=attack'
HTTP/2 200
…

If an admin is logged in to legacy.opencast.org and accidentally clicks this link, a user will silently be created.

CVE-2021-43807 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (9.10); upgrading removes the vulnerable code path.

Kodem intelligence

This issue is fixed in Opencast 9.10 and 10.0.

1. What is CVE-2021-43807? CVE-2021-43807 is a high-severity security vulnerability in org.opencastproject:opencast-common (maven), affecting versions < 9.10. It is fixed in 9.10.
2. How severe is CVE-2021-43807? CVE-2021-43807 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of org.opencastproject:opencast-common are affected by CVE-2021-43807? org.opencastproject:opencast-common (maven) versions < 9.10 is affected.
4. Is there a fix for CVE-2021-43807? Yes. CVE-2021-43807 is fixed in 9.10. Upgrade to this version or later.
5. Is CVE-2021-43807 exploitable, and should I be worried? Whether CVE-2021-43807 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2021-43807 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2021-43807? Upgrade org.opencastproject:opencast-common to 9.10 or later.