GHSA-c4gh-rv8h-q9vw

Source

https://github.com/advisories/GHSA-c4gh-rv8h-q9vw

Import Source

https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-c4gh-rv8h-q9vw/GHSA-c4gh-rv8h-q9vw.json

JSON Data

https://api.osv.dev/v1/vulns/GHSA-c4gh-rv8h-q9vw

Aliases

CVE-2026-53597

Published

2026-07-17T19:53:34Z

Modified

2026-07-17T20:00:17Z

Severity

8.7 (High) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N CVSS Calculator

Summary

Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader

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.

Database specific

{
    "cwe_ids":  [
        "CWE-94"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-07-17T19:53:34Z",
    "nvd_published_at":  "2026-07-16T16:19:12Z",
    "severity":  "HIGH"
}

References

Affected packages

npm / @prompty/core

Package

Name: @prompty/core; View open source insights on deps.dev
Purl: pkg:npm/%40prompty/core

Affected ranges

Type: SEMVER
Events: Introduced

2.0.0-alpha.1

Fixed

2.0.0-beta.3

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-c4gh-rv8h-q9vw/GHSA-c4gh-rv8h-q9vw.json"