Pydantic AI is a Python agent framework for building applications and workflows with Generative AI

Overview

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.77.0 until 1.107.7 and 2.52.0, the local web_fetch_tool and the WebFetch local fallback can consume excessive CPU and memory during HTML-to-Markdown conversion of attacker-controlled HTML containing deeply nested block elements. Conversion repeatedly reprocesses accumulated text and can greatly expand intermediate output before the returned-content limit is applied, allowing a model-directed fetch to delay other work in the process. Provider-native web fetching is not affected. This issue is fixed in versions 1.107.7 and 2.52.0.

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

Package advisory (CVE-2026-107287)

Affected packages:

• pydantic-ai >= 1.77.0, < 1.107.7
• pydantic-ai >= 2.0.0b1, < 2.52.0
• pydantic-ai-slim >= 1.77.0, < 1.107.7
• pydantic-ai-slim >= 2.0.0b1, < 2.52.0

Patched in:

• pydantic-ai 1.107.7
• pydantic-ai 2.52.0
• pydantic-ai-slim 1.107.7
• pydantic-ai-slim 2.52.0

Source: https://github.com/advisories/GHSA-v36g-jcw9-x7cw