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CVE

CVE-2026-73299

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

CVE-2026-73299

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

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 rendering, explicit renderer usage, unsafe member lookups, and attempted template function calls.

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
10
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
C
H
U
0
-
3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
C
H
U
-

Related Resources

No items found.

References

https://github.com/microsoft/prompty/security/advisories/GHSA-w28w-gp39-m4p6, https://github.com/microsoft/prompty/pull/404, https://github.com/microsoft/prompty/commit/047756f4c8caf91c5868eeb42520c938393277b0, https://github.com/microsoft/prompty

Severity

10

CVSS Score
0
10

Basic Information

Base CVSS
10
EPSS Probability
0.01215%
EPSS Percentile
0.6584%
Introduced Version
0,2.0.0-alpha.1
Fix Available
0.1.5,2.0.0-beta.5

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