Summary
Cross-Site Scripting in nunjucks
Affected versions of nunjucks do not properly escape specially structured user input in template vars when in auto-escape mode, resulting in a cross-site scripting vulnerability.
Proof of Concept
By using an array for the keys in a template var, escaping is bypassed.
name[]=<script>alert(1)</script>
A full PoC is available in the references section.
Impact
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Update to version 2.4.3 or later.
Frequently Asked Questions
- What is CVE-2016-10547? CVE-2016-10547 is a medium-severity cross-site scripting (XSS) vulnerability in nunjucks (npm), affecting versions < 2.4.3. It is fixed in 2.4.3. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of nunjucks are affected by CVE-2016-10547? nunjucks (npm) versions < 2.4.3 is affected.
- Is there a fix for CVE-2016-10547? Yes. CVE-2016-10547 is fixed in 2.4.3. Upgrade to this version or later.
- Is CVE-2016-10547 exploitable, and should I be worried? Whether CVE-2016-10547 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2016-10547 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2016-10547? Upgrade
nunjucksto 2.4.3 or later.