CVE-2021-23369 is a critical-severity (CVSS 9.8) remote code execution vulnerability in org.webjars:handlebars. 4 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-23369 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Remote code execution in handlebars when compiling templates
Real-World Exposure
org.webjars:handlebars☕org.webjars.npm:handlebars☕org.webjars.bowergithub.wycats:handlebars.js📦handlebarsReal-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 package handlebars before 4.7.7 are vulnerable to Remote Code Execution (RCE) when selecting certain compiling options to compile templates coming from an untrusted source.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.webjars:handlebars | all versions | 4.7.7 |
| ☕Maven | org.webjars.npm:handlebars | all versions | 4.7.7 |
| ☕Maven | org.webjars.bowergithub.wycats:handlebars.js | all versions | 4.7.7 |
| 📦npm | handlebars | all versions | 4.7.7 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…
The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…
The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…
The package handlebars before 4.7.7 are vulnerable to Remote Code Execut…
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.webjars:handlebars. 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.webjars:handlebars to 4.7.7 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-23369 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-2021-23369 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-2021-23369. 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.
Red Hat OpenShift Container Platform (OCP) 4 delivers the kibana package which includes Handlebars.js. From OCP 4.6, the kibana package is no longer shipped and will not be fixed. The openshift4/ose-logging-kibana6 container includes Handlebars.js directly as container first code. In OpenShift Container Platform…
Frequently Asked Questions
Is CVE-2021-23369 in your dependencies?
O3 detects CVE-2021-23369 across Maven, npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.