How severe is CVE-2016-4003?

CVE-2016-4003 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2016-4003?

CVE-2016-4003 affects the following packages: org.apache.struts:struts2-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2016-4003?

Update org.apache.struts:struts2-core to 2.3.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2016-4003 is resolved across your whole dependency graph.

How do I detect CVE-2016-4003 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.struts:struts2-core. 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.

How do I mitigate CVE-2016-4003 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2016-4003?

O3 pinpoints whether CVE-2016-4003 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2016-4003 actively exploited in the wild?

No public exploit code has been indexed for CVE-2016-4003 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2016-4003?

CVE-2016-4003 has an EPSS (Exploit Prediction Scoring System) score of 12.0%, placing it in the 96th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

What type of vulnerability is CVE-2016-4003?

CVE-2016-4003 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2016-4003 published, and has it been updated?

CVE-2016-4003 was published on April 12, 2016 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2016-4003: Cross-site Scripting in Apache Struts (Medium 6.…

EPSS Exploitation Probability

via FIRST.org ↗

12.0%probability of exploitation in next 30 days

Moderate Risk96th percentile+9.39%

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.

Blast Radius

1 pkg affected

☕org.apache.struts:struts2-core

Real-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

Cross-site scripting (XSS) vulnerability in the URLDecoder function in JRE before 1.8, as used in Apache Struts 2.x before 2.3.28, when using a single byte page encoding, allows remote attackers to inject arbitrary web script or HTML via multi-byte characters in a url-encoded parameter.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.struts:struts2-core`	≥ 2.0.0&&< 2.3.28	2.3.28

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.struts:struts2-core. 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.apache.struts:struts2-core to 2.3.28 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2016-4003 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-2016-4003 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-2016-4003. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

Cross-site scripting (XSS) vulnerability in the URLDecoder function in JRE before 1.8, as used in Apache Struts 2.x before 2.3.28, when using a single byte page encoding, allows remote attackers to inject arbitrary web script or HTML via multi-byte characters in a url-encoded parameter.

O3 Security · Impact-Aware SCA

Is CVE-2016-4003 in your dependencies?

O3 detects CVE-2016-4003 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2016-4003