CVE-2026-73299: Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer
Prompty is a markdown file format (.prompty) for LLM prompts. Prior to 0.1.5 and 2.0.0-beta.5, the TypeScript Nunjucks renderer evaluated untrusted .prompty template bodies with unrestricted JavaScript member access. An attacker-controlled template could traverse constructor and prototype properties to execute JavaScript in the host Node.js process. This issue is fixed in versions 0.1.5 and 2.0.0-beta.5.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 0.1.5 - Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 2.0.0-beta.5
Event History
Frequently Asked Questions
What is the severity of CVE-2026-73299?
CVE-2026-73299 has a critical severity score of 10.
How do I fix CVE-2026-73299?
To mitigate CVE-2026-73299, update your Prompty installation to version 0.1.5 or 2.0.0-beta.5 or later.
What type of vulnerability is CVE-2026-73299?
CVE-2026-73299 is a server-side template injection vulnerability that allows remote code execution.
What software is affected by CVE-2026-73299?
CVE-2026-73299 affects the Prompty @prompty/core Nunjucks Renderer.
What are the potential impacts of CVE-2026-73299?
Exploitation of CVE-2026-73299 could allow an attacker to gain control over the server and execute arbitrary code.