GHSA-v36g-jcw9-x7cw: Pydantic AI: Excessive resource use when local web fetching converts nested HTML

Summary

Applications using Pydantic AI's local web-fetch tool can suffer excessive CPU and memory use when converting attacker-controlled HTML. Nested block elements make the HTML-to-Markdown conversion reprocess accumulated text at each level, greatly expanding the intermediate output. Provider-native web fetching is not affected.

Mitigation

Upgrade to a patched release of `pydantic-ai` or `pydantic-ai-slim`. If you cannot upgrade yet, avoid using local web fetching for attacker-controlled HTML.

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