Handlebars RCE
Remote code execution via specially crafted templates
Severity CVSS
CRITICAL 9.8
Exploitation Shoulder
No known exploits
Fix available
No patch yet
Should I care?
This matters if:
- Apps using eval(), Function(), or dynamic code execution
- Template engines with expression support
Not relevant if:
- No dynamic code evaluation in your codebase
- All input is validated before processing
How to fix
How it breaks apps
1
User input reaches code evaluator
2
Dynamic code is constructed
3
Arbitrary code executes on server
4
Full server compromise
Affected packages
npm
Handlebars
Is this in your code?
Shoulder scans your codebase and tells you if CVE-2021-23383 is reachable — not just present.
npx @shoulderdev/cli trust .
Technical details
Risk by Environment
Production (public-facing)
HIGH
Patch soon. Exploitation requires specific conditions but impact is severe.
Staging
MEDIUM
Schedule patch. Review if this environment is network-accessible.
Internal services
MEDIUM
Assess exposure. Patch if the service handles sensitive data.
Local dev only
LOW
Minimal risk in isolated dev environments.
AI Development Risk
This vulnerability pattern is commonly introduced when AI generates code.
CWE-94
Code injection
AI-generated code commonly uses eval(), template literals, or dynamic function construction without sanitization.