A full PoC is available in the references section. Recommendation: Update to version 2.4.3 or later.","image":"https://o3.security/opengraph.png","datePublished":"2018-05-31T20:29:01.737Z","dateModified":"2026-10-20T10:47:12.454356936Z","url":"https://o3.security/vulnerability/CVE-2016-10547","inLanguage":"en","author":{"@id":"https://o3.security/#organization"},"publisher":{"@id":"https://o3.security/#organization"},"mainEntityOfPage":{"@type":"WebPage","@id":"https://o3.security/vulnerability/CVE-2016-10547"},"speakable":{"@type":"SpeakableSpecification","cssSelector":["h1",".vuln-summary",".vuln-severity",".vuln-mitigation"]},"about":[{"@type":"SoftwareApplication","name":"nunjucks","applicationCategory":"npm","softwareVersion":"2.4.3"}],"citation":[{"@type":"CreativeWork","name":"NVD","url":"https://nvd.nist.gov/vuln/detail/CVE-2016-10547"},{"@type":"CreativeWork","name":"OSV.dev","url":"https://osv.dev/vulnerability/CVE-2016-10547"},{"@type":"CreativeWork","name":"FIRST.org EPSS","url":"https://www.first.org/epss/api-data?cve=CVE-2016-10547"},{"@type":"CreativeWork","url":"https://github.com/advisories/GHSA-f7ph-p5rv-phw2"},{"@type":"CreativeWork","url":"https://www.npmjs.com/advisories/147"}]}A full PoC is available in the references section. Recommendation: Update to version 2.4.3 or later.","url":"https://o3.security/vulnerability/CVE-2016-10547","identifier":"CVE-2016-10547","datePublished":"2018-05-31T20:29:01.737Z","dateModified":"2026-10-20T10:47:12.454356936Z","inLanguage":"en","license":"https://creativecommons.org/licenses/by/4.0/","keywords":["CVE-2016-10547","MEDIUM severity","CWE-79","CVE","vulnerability","security advisory"],"creator":{"@id":"https://o3.security/#organization"},"isAccessibleForFree":true,"citation":[{"@type":"CreativeWork","name":"NVD","url":"https://nvd.nist.gov/vuln/detail/CVE-2016-10547"},{"@type":"CreativeWork","name":"OSV.dev","url":"https://osv.dev/vulnerability/CVE-2016-10547"},{"@type":"CreativeWork","name":"FIRST.org EPSS","url":"https://www.first.org/epss/api-data?cve=CVE-2016-10547"}],"variableMeasured":[{"@type":"PropertyValue","name":"CVSS Base Score","value":6.1,"description":"CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},{"@type":"PropertyValue","name":"Severity","value":"MEDIUM"},{"@type":"PropertyValue","name":"EPSS Percentile","value":73}]}\n```\n\nA full PoC is available in the references section.\n\n\n## Recommendation\n\nUpdate to version 2.4.3 or later."}},{"@type":"Question","name":"How severe is CVE-2016-10547?","acceptedAnswer":{"@type":"Answer","text":"CVE-2016-10547 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance."}},{"@type":"Question","name":"Which packages are affected by CVE-2016-10547?","acceptedAnswer":{"@type":"Answer","text":"CVE-2016-10547 affects the following packages: nunjucks (npm). Ecosystems affected: npm."}},{"@type":"Question","name":"How do I fix CVE-2016-10547?","acceptedAnswer":{"@type":"Answer","text":"Update nunjucks to 2.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2016-10547 is resolved across your whole dependency graph."}},{"@type":"Question","name":"How do I detect CVE-2016-10547 in my npm dependencies?","acceptedAnswer":{"@type":"Answer","text":"Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nunjucks, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version."}},{"@type":"Question","name":"How do I mitigate CVE-2016-10547 if there is no patch (or I can't update yet)?","acceptedAnswer":{"@type":"Answer","text":"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."}},{"@type":"Question","name":"Is CVE-2016-10547 actively exploited in the wild?","acceptedAnswer":{"@type":"Answer","text":"Yes. There are 3 known exploit references for CVE-2016-10547, including 3 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization."}},{"@type":"Question","name":"What is the EPSS score for CVE-2016-10547?","acceptedAnswer":{"@type":"Answer","text":"CVE-2016-10547 has an EPSS (Exploit Prediction Scoring System) score of 1.4%, placing it in the 73th 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 indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority."}},{"@type":"Question","name":"What type of vulnerability is CVE-2016-10547?","acceptedAnswer":{"@type":"Answer","text":"CVE-2016-10547 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."}},{"@type":"Question","name":"When was CVE-2016-10547 published, and has it been updated?","acceptedAnswer":{"@type":"Answer","text":"CVE-2016-10547 was published on May 31, 2018 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting."}}]}
NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
📦
📦 npm
Not in CISA KEV
MEDIUM severity

CVE-2016-10547 — nunjucks

MEDIUM

CVE-2016-10547 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in nunjucks. 3 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for nunjucks — see the affected versions and patch details below.

Cross-Site Scripting in nunjucks

Also known asGHSA-f7ph-p5rv-phw2
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
3 known
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.4%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs73th percentile — riskier than 73% of all scored CVEsHighest risk
0.00%0.65%1.29%1.94%0.4%1.4%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

3Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream
nunjucksnpm
5.0Mdownloads / week

Description

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.

Recommendation

Update to version 2.4.3 or later.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
📦npmnunjucksall versions2.4.3npm install nunjucks@2.4.3

Affected Products

1 product · 1 configurations
Application
nunjucksmozilla
≤ 2.4.2
range
Exploits & PoCs
3

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Nunjucks is a full featured templating engine for JavaScript. Versions 2…

nodesecurity.ioNVDOct 2019

Report on github.com

github.comNVDOct 2019

Report on github.com

github.comNVDOct 2019

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nunjucks, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update nunjucks to 2.4.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2016-10547 is resolved across your whole dependency graph.

  3. 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.

Frequently Asked Questions

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. ```javascript name[]=<script>alert(1)</script> ``` A full PoC is available in the references section. ## Recommendation Update to version 2.4.3 or later.
O3 Security · Impact-Aware SCA

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CVE-2016-10547: nunjucks XSS — Fixed in 2.4.3