Vulnerability details

CVE-2026-53597

Microsoft prompty

Prompty: Arbitrary code execution via JavaScript frontmatter in TypeScript loader

CVSS 4.0

8.7High

Official description

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.

CVSS scores

Score	Version	Source	Vector
8.7High	4.0	CVEProject cvelistV5 (CNA) (GitHub_M)	`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`

Affected products

Vendor	Product	Versions	Source
Microsoft	prompty	>= 2.0.0-alpha.1, < 2.0.0-beta.3	CVEProject cvelistV5 (CNA)

References and advisories

https://github.com/microsoft/prompty/security/advisories/GHSA-c4gh-rv8h-q9vw x_refsource_CONFIRM
https://github.com/microsoft/prompty/commit/c27402da2487075be577f06aa79df627fb9d6853 x_refsource_MISC

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Details

Published: 2026-07-16
Last updated: 2026-07-18
State: Published
Assigner (CNA): GitHub_M

Exploit prediction (EPSS)

0.97%

Probability of exploitation in 30 days

62.1%

Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable: No
Exploitation: None
Technical impact: Partial

Weaknesses (CWE)

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