Is CVE-2026-73299 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-73299 being exploited in the wild.

How severe is CVE-2026-73299?

Critical severity, with a CVSS score of 10, published 12 August 2026.

Which products and versions are affected?

Microsoft Prompty ≤0.1.4, ≤2.0.0-beta.4.

Is there a fix for CVE-2026-73299?

A patch was published on 2026-07-24: Patched in @prompty/core 0.1.5 and 2.0.0-beta.5 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-73299 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-73299?

Check whether you run Microsoft Prompty at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-73299: Microsoft Prompty server-side template injection to RCE in Nunjucks renderer

CVE-2026-73299 · Severity: critical · CVSS 10 · Published 2026-08-12

Microsoft Prompty is a framework for building applications that work with language models using template files. The Nunjucks template renderer in the TypeScript runtime fails to properly sanitize untrusted template input, allowing attackers to execute arbitrary JavaScript code on the host system with full privileges. Applications that render untrusted .prompty files from community sources, LLM outputs, or user uploads are at immediate risk of complete system compromise.

Technologies: Microsoft Prompty. Vendors: Microsoft.

Quick answers

Is CVE-2026-73299 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-73299 being exploited in the wild.
How severe is CVE-2026-73299?: Critical severity, with a CVSS score of 10, published 12 August 2026.
Which products and versions are affected?: Microsoft Prompty ≤0.1.4, ≤2.0.0-beta.4.
Is there a fix for CVE-2026-73299?: A patch was published on 2026-07-24: Patched in @prompty/core 0.1.5 and 2.0.0-beta.5 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-73299 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-73299?: Check whether you run Microsoft Prompty at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability is a server-side template injection (SSTI) in the @prompty/core Nunjucks renderer affecting versions ≤0.1.4 and ≤2.0.0-beta.4. The renderer evaluates untrusted template bodies with unrestricted JavaScript member access, allowing attackers to traverse constructor and prototype properties via template expressions to execute arbitrary code in the Node.js host process. No authentication or user interaction is required; an attacker merely supplies a malicious .prompty file. The attack vector is network-based with low complexity. Patches are available in @prompty/core 0.1.5 and 2.0.0-beta.5, which sanitize inputs to own-data-only values and reject constructor/prototype traversal.

Affected products

Microsoft Prompty ≤0.1.4, ≤2.0.0-beta.4

Identifiers

CVE-2026-73299
GHSA-w28w-gp39-m4p6

Timeline

2026-07-24: disclosed
2026-07-24: patched: Patched in @prompty/core 0.1.5 and 2.0.0-beta.5

References

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