CVE-2026-107288: Pydantic Pydantic-Ai

Low severity, CVSS 3.7. EPSS: 0.4% chance of exploitation in the next 30 days.

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.77.0 until 1.107.6 and 2.44.0, the local web_fetch_tool and the WebFetch local fallback compare blocked_domains entries with a URL hostname before both values are normalized to the form used by getaddrinfo. An attacker-influenced model can use an equivalent IDNA spelling, non-ASCII label separator, case variation, or trailing root label that resolves to a blocked host but does not match the configured string, causing the application to fetch that host with its own privileges. allowed_domains fails closed for unmatched spellings, and private-IP and cloud-metadata protections remain effective. This issue is fixed in versions 1.107.6 and 2.44.0.

Affected products

• Pydantic Pydantic-Ai: from 1.77.0, before 1.107.6 (fixed in 1.107.6); from 2.0.0b1, before 2.44.0 (fixed in 2.44.0)
• Pydantic Pydantic-Ai-Slim: from 1.77.0, before 1.107.6 (fixed in 1.107.6); from 2.0.0b1, before 2.44.0 (fixed in 2.44.0)

Published 2026-10-08. Last modified 2026-10-08.