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CVE-2026-25640PYSEC-2026-2979GHSA-WJP5-868J-WQV7PYSEC-2026-2983

Pydantic AI affected by Stored XSS via Path Traversal in Web UI CDN URL

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 1.51.0
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • pydantic pydantic-ai

    From 1.34.0 · fixed in 1.51.0

  • pydantic-aiPyPI

    From 1.34.0 · fixed in 1.51.0

  • pydantic-ai-slimPyPI

    From 1.34.0 · fixed in 1.51.0

References 2

GitHub · pydantic/pydantic-ai