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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

10.0 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS

• CVE-2026-73299: 1.78% estimated exploitation activity in the next 30 days; percentile 78.32 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary 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. Affected packages - npm @prompty/core versions <= 0.1.4 - npm @prompty/core versions <= 2.0.0-beta.4 Impact Applications that render untrusted, community-supplied, cloned, or LLM-generated .prompty files with the TypeScript runtime could allow attacker-controlled code execution with the privileges of the Node.js host process. Remediation Upgrade to @prompty/core 2.0.0-beta.5 or later. The patched renderer sanitizes render inputs to own-data-only values, rejects constructor/prototype member traversal, and disallows template function calls. Ordinary interpolation, conditionals, loops, and own nested data properties remain supported. Fix details The fix is merged in PR #404 and includes regression coverage for default Nunjucks…

Published by the source

24 Jul 2026, 16:23 UTC

Last modified by the source

13 Aug 2026, 04:11 UTC

Source last checked

26 Oct 2026, 12:58 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w28w-gp39-m4p6

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-w28w-gp39-m4p6

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-w28w-gp39-m4p6

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# Patch Next advisory brief: CVE-2026-73299

Advisory: Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer
IDs: CVE-2026-73299, GHSA-w28w-gp39-m4p6
Record: https://patchnext.com/advisories/ghsa-w28w-gp39-m4p6 (revision 3, source checked 26 Oct 2026, 12:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 10.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @prompty/core 2.0.0-beta.5, 0.1.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @prompty/core: affected <= 0.1.4; >= 2.0.0-alpha.1, <= 2.0.0-beta.4; fixed in 0.1.5, 2.0.0-beta.5

## Suggested inspection (read-only)
- `npm ls @prompty/core --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @prompty/core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-w28w-gp39-m4p6 (GitHub-reviewed advisory GHSA-w28w-gp39-m4p6 lists affected ranges: npm @prompty/core >=0 =2.0.0-alpha.1 <=2.0.0-beta.4)
- Verified: https://osv.dev/vulnerability/GHSA-w28w-gp39-m4p6 (OSV record GHSA-w28w-gp39-m4p6 lists affected ranges: npm @prompty/core >=0 =2.0.0-alpha.1 <2.0.0-beta.5 (fixed))

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