CVE-2021-43807 is a medium-severity (CVSS 6.5) CWE-290 vulnerability in org.opencastproject:opencast-common. 1 public exploit reference exists, so weaponization risk is real. A fix is available for org.opencastproject:opencast-common — see the affected versions and patch details below.
HTTP Method Spoofing
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2021-43807 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,567 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.opencastproject:opencast-commonReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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.
Impact
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.
Patches
This issue is fixed in Opencast 9.10 and 10.0.
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
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]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.opencastproject:opencast-common | all versions | 9.10org.opencastproject:opencast-common:9.10 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.opencastproject:opencast-common, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.opencastproject:opencast-common to 9.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-43807 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2021-43807 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2021-43807. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2021-43807 in your dependencies?
O3 Security finds CVE-2021-43807 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.