CVE-2020-5529 is a high-severity (CVSS 8.1) CWE-665 vulnerability in net.sourceforge.htmlunit:htmlunit. A fix is available for net.sourceforge.htmlunit:htmlunit — see the affected versions and patch details below.
Code execution vulnerability in HtmlUnit
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2020-5529.
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-2020-5529 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
net.sourceforge.htmlunit:htmlunitReal-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
HtmlUnit prior to 2.37.0 contains code execution vulnerabilities. HtmlUnit initializes Rhino engine improperly, hence a malicious JavScript code can execute arbitrary Java code on the application. Moreover, when embedded in Android application, Android-specific initialization of Rhino engine is done in an improper way, hence a malicious JavaScript code can execute arbitrary Java code on the application.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | net.sourceforge.htmlunit:htmlunit | all versions | 2.37.0net.sourceforge.htmlunit:htmlunit:2.37.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for net.sourceforge.htmlunit:htmlunit, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update net.sourceforge.htmlunit:htmlunit to 2.37.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5529 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-2020-5529 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-5529. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Frequently Asked Questions
Is CVE-2020-5529 in your dependencies?
O3 Security finds CVE-2020-5529 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.