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OpenAdvisories
High · 7.6 CVE-2026-107295 EUVD-2026-95106GHSA-h4xc-3qfq-jf93PYSEC-2026-4278PYSEC-2026-4287

`pydantic-ai-slim` web UI `/api/chat` accepts browser-simple cross-origin requests that can trigger agent tool execution

Published Oct 8, 2026 · Updated Oct 8, 2026 · Assigned by GitHub_M

Vendor: pydantic Product: pydantic-ai Product: pydantic-ai-slim Package: pydantic-ai Package: pydantic-ai-slim Ecosystem: PyPI

Description

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.

Affected products

VendorProductAffectedFixed
pydantic pydantic-ai >= 1.34.0, < 1.107.4, >= 2.0.0b1, < 2.28.0 —
pydantic pydantic-ai-slim >= 1.34.0, < 1.107.4, >= 2.0.0b1, < 2.28.0 —

Affected packages

EcosystemPackageAffectedFixedRecord
PyPI pydantic-ai >= 1.34.0, < 1.107.4 1.107.4 GHSA-h4xc-3qfq-jf93
PyPI pydantic-ai >= 2.0.0b1, < 2.28.0 2.28.0 GHSA-h4xc-3qfq-jf93
PyPI pydantic-ai >= 1.34.0, < 1.107.4 · >= 2.0.0b1, < 2.28.0 1.107.4, 2.28.0 PYSEC-2026-4278
PyPI pydantic-ai-slim >= 1.34.0, < 1.107.4 1.107.4 GHSA-h4xc-3qfq-jf93
PyPI pydantic-ai-slim >= 2.0.0b1, < 2.28.0 2.28.0 GHSA-h4xc-3qfq-jf93
PyPI pydantic-ai-slim >= 1.34.0, < 1.107.4 · >= 2.0.0b1, < 2.28.0 1.107.4, 2.28.0 PYSEC-2026-4287

References