Vulnerability-Lookup

GHSA-C4GH-RV8H-Q9VW

Vulnerability from github – Published: 2026-07-17 19:53 – Updated: 2026-07-17 19:53

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.

Severity

8.7 (High)


                  
                    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

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@prompty/core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0-alpha.1"
            },
            {
              "fixed": "2.0.0-beta.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-53597"
  ],
  "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"
  },
  "details": "## Summary\nThe 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.\n\n## Affected package\n- npm `@prompty/core` v2 prerelease line: `\u003e= 2.0.0-alpha.1 \u003c 2.0.0-beta.3`\n- Fixed in `@prompty/core@2.0.0-beta.3`\n\nThe 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`.\n\n## Impact\nApplications 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.\n\n## Remediation\nUpgrade `@prompty/core` to `2.0.0-beta.3` or later.\n\nThe 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.\n\n## Fix details\nFixed by commit `c27402da2487075be577f06aa79df627fb9d6853` and released via `typescript/2.0.0-beta.3`.",
  "id": "GHSA-c4gh-rv8h-q9vw",
  "modified": "2026-07-17T19:53:34Z",
  "published": "2026-07-17T19:53:34Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/microsoft/prompty/security/advisories/GHSA-c4gh-rv8h-q9vw"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53597"
    },
    {
      "type": "WEB",
      "url": "https://github.com/microsoft/prompty/commit/c27402da2487075be577f06aa79df627fb9d6853"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/microsoft/prompty"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader"
}

CVE-2026-53597 (GCVE-0-2026-53597)

Vulnerability from cvelistv5 – Published: 2026-07-16 14:54 – Updated: 2026-07-18 02:51

Title

Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader

Summary

Prompty is a markdown file format (.prompty) for LLM prompts. From 2.0.0-alpha.1 until 2.0.0-beta.3, the @prompty/core TypeScript loader in runtime/typescript/packages/core/src/core/loader.ts used gray-matter without overriding executable js and javascript frontmatter engines, allowing an attacker-controlled .prompty file with ---js frontmatter to execute arbitrary JavaScript during prompt loading. This issue is fixed in version 2.0.0-beta.3.

Severity

8.7 (High)


                        
                          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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-18 02:50 UTC

CWE

CWE-94 - Improper Control of Generation of Code ('Code Injection')

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7592 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/microsoft/prompty/security/adv…	x_refsource_CONFIRM
https://github.com/microsoft/prompty/commit/c2740…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
microsoft	prompty	Affected: >= 2.0.0-alpha.1, < 2.0.0-beta.3

Show details on NVD website

JSON

To clipboard

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  "containers": {
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      {
        "metrics": [
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            "other": {
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                "id": "CVE-2026-53597",
                "options": [
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                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-18T02:50:54.007782Z",
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          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
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    "cna": {
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        {
          "product": "prompty",
          "vendor": "microsoft",
          "versions": [
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        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 8.7,
            "baseSeverity": "HIGH",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "PASSIVE",
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            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "HIGH",
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      "references": [
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      "source": {
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  "cveMetadata": {
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    "datePublished": "2026-07-16T14:54:55.075Z",
    "dateReserved": "2026-06-09T19:39:52.404Z",
    "dateUpdated": "2026-07-18T02:51:03.900Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-C4GH-RV8H-Q9VW

Summary

Affected package

Impact

Remediation

Fix details

CVE-2026-53597 (GCVE-0-2026-53597)

Tags

Sightings

Nomenclature

Related by attack behaviour