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OpenAdvisories
Medium · 6.4 CVE-2026-107292 EUVD-2026-95099GHSA-q2xc-rrxj-58x9PYSEC-2026-4279PYSEC-2026-4288

Pydantic AI Web chat UI (`Agent.to_web()`, `clai web`): the local chat endpoint does not validate the `Host` header

Published Oct 8, 2026 · Updated Oct 14, 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 2.30.0, the Agent.to_web() and clai web development chat server does not validate the Host header, allowing a website visited by a developer to use DNS rebinding to reach a loopback-hosted agent as a same-origin service. The hostile page can read the served UI and submit chat requests that execute agent tools with the local process's privileges and credentials, causing data disclosure or unwanted side effects. Binding to localhost, Origin checks, and CSRF tokens do not prevent the same-origin DNS rebinding path. This issue is fixed in versions 1.107.5 and 2.30.0.

Affected products

VendorProductAffectedFixed
pydantic pydantic-ai >= 1.34.0, < 2.0.0b1, >= 2.0.0b1, < 2.30.0 —
pydantic pydantic-ai-slim >= 1.34.0, < 2.0.0b1, >= 2.0.0b1, < 2.30.0 —

Affected packages

EcosystemPackageAffectedFixedRecord
PyPI pydantic-ai >= 1.34.0, < 1.107.5 1.107.5 GHSA-q2xc-rrxj-58x9
PyPI pydantic-ai >= 2.0.0b1, < 2.30.0 2.30.0 GHSA-q2xc-rrxj-58x9
PyPI pydantic-ai >= 1.34.0, < 1.107.5 · >= 2.0.0b1, < 2.30.0 1.107.5, 2.30.0 PYSEC-2026-4279
PyPI pydantic-ai-slim >= 1.34.0, < 1.107.5 1.107.5 GHSA-q2xc-rrxj-58x9
PyPI pydantic-ai-slim >= 2.0.0b1, < 2.30.0 2.30.0 GHSA-q2xc-rrxj-58x9
PyPI pydantic-ai-slim >= 1.34.0, < 1.107.5 · >= 2.0.0b1, < 2.30.0 1.107.5, 2.30.0 PYSEC-2026-4288

References