What’s Vulnerable › Vulnerabilities

CVE-2026-73299: Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer

• Severity: critical (CVSS 10.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-12 · updated 2026-10-24
• Weakness: CWE-94

Description

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 products

• microsoft prompty: before 0.1.5; from 2.0.0-alpha.1, < 2.0.0-beta.5

References

• https://github.com/microsoft/prompty/commit/e4a0ebf49e3a78d5d7796c8480bf9a4f0c54d19e
• https://github.com/microsoft/prompty/commit/f5c57c94a0990cca79d095c3daab661b4b1fb89f
• https://github.com/microsoft/prompty/pull/404
• https://github.com/microsoft/prompty/pull/405
• https://github.com/microsoft/prompty/security/advisories/GHSA-w28w-gp39-m4p6
• https://github.com/microsoft/prompty/tree/typescript/2.0.0-beta.5

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