High · published October 8, 2026
Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.34.0 until 1.107.4 and 2.28.0, the Agent.to_web() and clai web development chat endpoint has missing request content-type validation. A website visited by a developer can submit a browser-compatible request to a loopback-hosted chat server, causing the served agent to run and execute tools with the privileges and credentials of the local process; client-relayed approval decisions also leave requires_approval=True tools exposed. Binding to localhost does not prevent a browser page from reaching the loopback address. This issue is fixed in versions 1.107.4 and 2.28.0.
| Product | Versions | Fixed in |
|---|---|---|
| pydantic/pydantic_ai | ≥ 1.34.0, < 1.107.4 | 1.107.4 |
| pydantic/pydantic_ai | ≥ 2.0.0, < 2.28.0 | 2.28.0 |