CVE-2021-32623 is a medium-severity (CVSS 6.5) CWE-776 vulnerability in org.opencastproject:opencast-kernel. 1 public exploit reference exists, so weaponization risk is real. O3 Security confirms whether CVE-2021-32623 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Billion laughs attack (XML bomb)
Real-World Exposure
org.opencastproject:opencast-kernelReal-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 is a free and open source solution for automated video capture and distribution. Versions of Opencast prior to 9.6 are vulnerable to the billion laughs attack, which allows an attacker to easily execute a (seemingly permanent) denial of service attack, essentially taking down Opencast using a single HTTP request. To exploit this, users need to have ingest privileges, limiting the group of potential attackers The problem has been fixed in Opencast 9.6. There is no known workaround for this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.opencastproject:opencast-kernel | all versions | 9.6 |
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-kernel. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.opencastproject:opencast-kernel to 9.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32623 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 pinpoints whether CVE-2021-32623 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2021-32623. 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-2021-32623 in your dependencies?
O3 detects CVE-2021-32623 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.