CVE-2020-13959 — velocity-tools-parent
MEDIUMCVE-2020-13959 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in org.apache.velocity.tools:velocity-tools-parent. A fix is available for org.apache.velocity.tools:velocity-tools-parent — see the affected versions and patch details below.
Cross-site scripting (XSS) in Apache Velocity Tools
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2020-13959 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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 | 3.1org.apache.velocity.tools:velocity-tools-parent:3.1 |
| ☕Maven | org.apache.velocity:velocity-tools | all versions | No fix |
Affected Products
velocity toolsapachedebian linuxdebianDetection & 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
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?
Find it across Maven, including transitive dependencies.