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CVE-2026-25640

CVE-2026-25640 · Pydantic AI affected by Stored XSS via Path Traversal in Web UI CDN URL

This page contains facts from public vulnerability sources. Check the original advisory before updating.

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.34.0 to before 1.51.0, a path traversal vulnerability in the Pydantic AI web UI allows an attacker to serve arbitrary JavaScript in the context of the application by crafting a malicious URL. In affected versions, the CDN URL is constructed using a version query parameter from the request URL. This parameter is not validated, allowing path traversal sequences that cause the server to fetch and serve attacker-controlled HTML/JavaScript from an arbitrary source on the same CDN, instead of the legitimate chat UI package. If a victim clicks the link or visits it via an iframe, attacker-controlled code executes in their browser, enabling theft of chat history and other client-side data. This vulnerability only affects applications that use Agent.to_web to serve a chat interface and clai web to serve a chat interface from the CLI. These are typically run locally (on localhost), but may also be deployed on a remote server. This vulnerability is fixed in 1.51.0.

CVSS 7.1 · High · EPSS 0.4% · Fix available

Published
Updated

Stack: python

Affected products and versions

  • pydantic-ai

    Versions
    • >= 1.34.0, < 1.51.0: Affected

    No fix published

  • pydantic-ai PyPI

    Versions
    • 1.34.0
    • 1.35.0
    • 1.36.0
    • 1.37.0
    • 1.38.0
    • 1.39.0
    • 1.39.1
    • 1.40.0
    • 1.41.0
    • 1.42.0
    • 1.43.0
    • 1.44.0
    • 1.46.0
    • 1.47.0
    • 1.48.0
    • 1.49.0
    • 1.50.0
    Affected ranges
    • ECOSYSTEM: ≥ 1.34.0, < 1.51.0

    Update to 1.51.0

  • pydantic-ai-slim PyPI

    Versions
    • 1.34.0
    • 1.35.0
    • 1.36.0
    • 1.37.0
    • 1.38.0
    • 1.39.0
    • 1.39.1
    • 1.40.0
    • 1.41.0
    • 1.42.0
    • 1.43.0
    • 1.44.0
    • 1.46.0
    • 1.47.0
    • 1.48.0
    • 1.49.0
    • 1.50.0
    Affected ranges
    • ECOSYSTEM: ≥ 1.34.0, < 1.51.0

    Update to 1.51.0

Original sources

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