CVE-2026-53597

Summary

Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader

Severity

high

EPSS

1.0% (p62)

CWE

CWE-94

Also known as

GHSA-c4gh-rv8h-q9vw

Published

2026-07-17

Updated

2026-07-17

Advisory details

Summary

The TypeScript Prompty loader used gray-matter without overriding executable frontmatter engines. gray-matter supports JavaScript frontmatter blocks such as ---js and evaluates them while parsing. An attacker-controlled .prompty file could therefore execute arbitrary JavaScript during prompt loading.

Affected package

• npm @prompty/core v2 prerelease line: >= 2.0.0-alpha.1 < 2.0.0-beta.3
• Fixed in @prompty/core@2.0.0-beta.3

The legacy v1 JavaScript runtime had a historical hardening change for this issue. During the v2 TypeScript runtime rebuild, the loader again called gray-matter directly and the vulnerable behavior was present in the v2 prerelease packages until 2.0.0-beta.3.

Impact

Applications that load untrusted .prompty files, user-provided prompt paths, or prompt bundles from less-trusted locations could execute arbitrary JavaScript in the host Node.js process during frontmatter parsing.

Remediation

Upgrade @prompty/core to 2.0.0-beta.3 or later.

The fix explicitly overrides the js and javascript gray-matter engines and rejects JavaScript frontmatter in .prompty files. Prompty frontmatter is YAML-only; executable frontmatter is unsupported. A regression test now verifies that ---js frontmatter is rejected and not evaluated.

Fix details

Fixed by commit c27402da2487075be577f06aa79df627fb9d6853 and released via typescript/2.0.0-beta.3.

References

• https://github.com/advisories/GHSA-c4gh-rv8h-q9vw
• https://github.com/microsoft/prompty/security/advisories/GHSA-c4gh-rv8h-q9vw
• https://nvd.nist.gov/vuln/detail/CVE-2026-53597
• https://github.com/microsoft/prompty/commit/c27402da2487075be577f06aa79df627fb9d6853

Related advisories

• GHSA-w28w-gp39-m4p6 — critical · npm/@prompty/core
• CVE-2026-114125 — critical · npm/storybook
• CVE-2026-107806 — critical · Go/github.com/0xJacky/Nginx-UI
• CVE-2026-106446 — critical · npm/handlebars
• CVE-2026-61447 — critical · PyPI/praisonaiagents
• CVE-2026-105857 — critical · npm/@payloadcms/plugin-form-builder
• CVE-2026-73487 — critical · npm/flowise
• CVE-2026-62176 — critical · PyPI/PraisonAI

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