CVE-2020-13959
MEDIUMCVE-2020-13959 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in org.apache.velocity.tools:velocity-tools-parent. O3 Security confirms whether CVE-2020-13959 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Cross-site scripting (XSS) in Apache Velocity Tools
Real-World Exposure
org.apache.velocity.tools:velocity-tools-parent☕org.apache.velocity:velocity-toolsReal-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
The default error page for VelocityView in Apache Velocity Tools prior to 3.1 reflects back the vm file that was entered as part of the URL. An attacker can set an XSS payload file as this vm file in the URL which results in this payload being executed. XSS vulnerabilities allow attackers to execute arbitrary JavaScript in the context of the attacked website and the attacked user. This can be abused to steal session cookies, perform requests in the name of the victim or for phishing attacks.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.velocity.tools:velocity-tools-parent | all versions | 3.1 |
| ☕Maven | org.apache.velocity:velocity-tools | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.velocity.tools:velocity-tools-parent. 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.velocity.tools:velocity-tools-parent to 3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-13959 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-2020-13959 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-2020-13959. 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-2020-13959 in your dependencies?
O3 detects CVE-2020-13959 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.