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CVE-2026-53598: CVE-2026-53598: Arbitrary File Read via File Reference Expansion in Microsoft Prompty

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CVE-2026-53598: Arbitrary File Read via File Reference Expansion in Microsoft Prompty

Vulnerability ID: CVE-2026-53598
CVSS Score: 7.5
Published: 2026-07-17

CVE-2026-53598 is a directory traversal and arbitrary file read vulnerability in Microsoft Prompty ecosystem loaders across multiple languages. Prior to version 2.0.0-beta.2, the loaders resolved ${file:...} reference strings inside frontmatter configuration blocks without enforcing that the target file paths resided within authorized directories. This deficiency allows an attacker-controlled configuration file to read sensitive operating system and application files through absolute paths, directory traversal, or symbolic link escapes. The issue is addressed across the Python, C#, Node.js/TypeScript, and Rust ecosystems.

TL;DR

Microsoft Prompty loaders before 2.0.0-beta.2 are vulnerable to arbitrary file read via directory traversal, absolute paths, or symbolic link escapes within frontmatter ${file:...} sequence expansions.

⚠️ Exploit Status: POC

Technical Details

  • CWE ID: CWE-22 / CWE-200
  • Attack Vector: Network (AV:N)
  • CVSS v3.1: 7.5 (High)
  • EPSS Score: 1.057% (60.65th percentile)
  • Exploit Status: Proof-of-Concept (PoC) Available
  • Impact: Arbitrary File Read (Confidentiality: High)
  • CISA KEV: Not Listed

Affected Systems

  • Microsoft Prompty Python Loader (prompty)
  • Microsoft Prompty C# Loader (Prompty.Core)
  • Microsoft Prompty TypeScript Loader (@prompty/core)
  • Microsoft Prompty Rust Loader (prompty)
  • prompty (Python): < 2.0.0b2 (Fixed in: 2.0.0b2)
  • Prompty.Core (C#): < 2.0.0-beta.2 (Fixed in: 2.0.0-beta.2)
  • @prompty/core (Node.js): < 2.0.0-beta.2 (Fixed in: 2.0.0-beta.2)
  • prompty (Rust): < 2.0.0-beta.2 (Fixed in: 2.0.0-beta.2)

Code Analysis

Commit: 88ac994

Fix reference expansion path traversal vulnerabilities across Python, C#, Node.js, and Rust

C# / Python / TypeScript security validations added to verify candidate path canonicalization within authorized root paths.
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Exploit Details

  • GitHub Fix Commit Tests: The patch tests include complete replication scenarios demonstrating absolute path, symlink, and relative path escape failures.

Mitigation Strategies

  • Upgrade Microsoft Prompty libraries to version 2.0.0-beta.2 or higher
  • Restrict application upload capabilities for .prompty extension files from untrusted actors
  • Sanitize input paths and ensure least privilege runtime execution to limit access scope of the application process

Remediation Steps:

  1. Identify all applications utilizing the prompty, Prompty.Core, @prompty/core, or Rust prompty packages
  2. Configure dependency files (requirements.txt, package.json, .csproj, Cargo.toml) to demand version 2.0.0-beta.2 or above
  3. Run local dependency scanning or vulnerability assessment tools to verify the remediation is applied
  4. Review application load configurations and explicitly specify allowed_file_roots only when necessary

References

Read the full report for CVE-2026-53598 on our website for more details including interactive diagrams and full exploit analysis.

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