CVE-2026-73299: Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 1.8%
EPSS score, percentile 78.2 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 10.0 Critical
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- < 0.1.5
- >= 2.0.0-alpha.1, < 2.0.0-beta.5
Source: CISA KEV 2026.10.28, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | < 0.1.5 |
| Affected | >= 2.0.0-alpha.1, < 2.0.0-beta.5 |
Source: CVE List, as of . About the data.
About this vulnerability
Prompty is a markdown file format (.prompty) for LLM prompts. Prior to 0.1.5 and 2.0.0-beta.5, 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. This issue is fixed in versions 0.1.5 and 2.0.0…
Summary: CVE record, as of .
- CISA has not added CVE-2026-73299 to its Known Exploited Vulnerabilities (KEV) catalog, as of 28 Oct 2026.
- The CVE record was published on 12 Aug 2026.
- The CVE record carries a CVSS v3.1 base score of 10.0 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 1.8% (percentile 78.2), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable yes, technical impact total.
Source: CISA KEV 2026.10.28, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
Prompty: Server-Side Template Injection to Remote Code Execution in the @prompty/core Nunjucks Renderer
Prompty is a markdown file format (.prompty) for LLM prompts. Prior to 0.1.5 and 2.0.0-beta.5, 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. This issue is fixed in versions 0.1.5 and 2.0.0-beta.5.
Source: CVE List, as of . About the data.
Weakness
CWE-94, CWE-1336
- CWE-94: Improper Control of Generation of Code ('Code Injection')
- CWE-1336: Improper Neutralization of Special Elements Used in a Template Engine
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published |
References
6
- https://github.com/microsoft/prompty/security/advisories/GHSA-w28w-gp39-m4p6
- https://github.com/microsoft/prompty/pull/404
- https://github.com/microsoft/prompty/pull/405
- https://github.com/microsoft/prompty/commit/e4a0ebf49e3a78d5d7796c8480bf9a4f0c54d19e
- https://github.com/microsoft/prompty/commit/f5c57c94a0990cca79d095c3daab661b4b1fb89f
- https://github.com/microsoft/prompty/tree/typescript/2.0.0-beta.5
Known exploited Microsoft vulnerabilities
- CVE-2026-96951: Microsoft Windows Command Injection Vulnerability
- CVE-2026-65660: Microsoft SharePoint Code Injection Vulnerability
- CVE-2026-81963: Microsoft Windows Link Following Vulnerability
- CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability
- CVE-2019-1068: Microsoft SQL Server Remote Code Execution Vulnerability