What’s Vulnerable › Vulnerabilities

CVE-2026-107287: Pydantic AI: Excessive resource use when local web fetching converts nested HTML

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-08 · updated 2026-10-14
• Weakness: CWE-400

Description

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.

Affected products

• pydantic-ai: from 1.77.0 before 1.107.7; from 2.0.0 before 2.52.0 — fixed in 1.107.7, 2.52.0

How to fix

Upgrade to a fixed version: pydantic-ai 1.107.7, 2.52.0. Check the vendor advisory for mitigations.

References

• https://github.com/pydantic/pydantic-ai/commit/2b247add4950bef61d352e7ca8aefbd20539180c
• https://github.com/pydantic/pydantic-ai/commit/2fd38792693da00a3ca5412aeffb436787af3545
• https://github.com/pydantic/pydantic-ai/pull/8984
• https://github.com/pydantic/pydantic-ai/pull/8985
• https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.7
• https://github.com/pydantic/pydantic-ai/releases/tag/v2.52.0
• https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-v36g-jcw9-x7cw

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