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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
Required
User action required
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products
pydantic:pydantic-ai-slim
pydantic:pydantic-ai
References 7
https://github.com/pydantic/pydantic-ai/commit/2b247add4950bef61d352e7ca8aefbd2…
security-advisories@github.com
https://github.com/pydantic/pydantic-ai/commit/2fd38792693da00a3ca5412aeffb4367…
security-advisories@github.com
https://github.com/pydantic/pydantic-ai/pull/8984
security-advisories@github.com
https://github.com/pydantic/pydantic-ai/pull/8985
security-advisories@github.com
https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.7
security-advisories@github.com
https://github.com/pydantic/pydantic-ai/releases/tag/v2.52.0
security-advisories@github.com
https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-v36g-jcw9-x7cw
security-advisories@github.com