CVE-2026-107290
Received Received - Intake

Denial of Service in Pydantic AI Framework

Publication date: 2026-10-08

Last updated on: 2026-10-08

Assigner: GitHub, Inc.

Description
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 process server-controlled responses with quadratic title extraction, whitespace normalization, and ordered-list numbering. An attacker-controlled page of modest size can therefore block the event loop for an extended period, stalling other agent runs and requests, while unsupported codecs or excessive HTML or JSON nesting can abort an individual run. This issue is fixed in versions 1.107.6 and 2.44.0.

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Meta Information

Published
2026-10-08
Last Modified
2026-10-08
Generated
2026-10-08
AI Q&A
2026-10-08
EPSS Evaluated
N/A
NVD
CVE-2026-107290
EUVD
EUVD-2026-95093

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
pydantic pydantic-ai >= 1.77.0, < 1.107.6
pydantic pydantic-ai >= 2.0.0b1, < 2.44.0
pydantic pydantic-ai-slim >= 1.77.0, < 1.107.6
pydantic pydantic-ai-slim >= 2.0.0b1, < 2.44.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-1333 The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.

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Executive Summary

This vulnerability in Pydantic AI allows an attacker to craft a malicious web page that can block the event loop due to quadratic title extraction, whitespace normalization, and ordered-list numbering. This causes delays in agent runs and requests, potentially stalling the system.

Detection Guidance

This vulnerability is specific to Pydantic AI versions between 1.77.0 and 1.107.6 (excluding 1.107.6) and 2.44.0. Check installed versions with pip show pydantic-ai or pip list | grep pydantic-ai. If affected, update to versions 1.107.6 or 2.44.0 or later.

Impact Analysis

If exploited, this vulnerability can cause denial-of-service by stalling agent runs and requests. It may also lead to crashes if unsupported codecs or excessive HTML/JSON nesting are used in the attack.

Compliance Impact

This vulnerability primarily impacts system availability by allowing denial-of-service through event loop stalls. While it does not directly expose or leak data, prolonged service disruptions could interfere with logging, monitoring, or audit processes required by GDPR and HIPAA. Compliance may be affected if systems fail to maintain availability for data processing or fail to log events during outages.

Mitigation Strategies

Upgrade Pydantic AI to version 1.107.6 or 2.44.0 or later immediately. If upgrading is not possible, disable the web_fetch_tool feature or restrict access to untrusted sources to prevent exploitation.

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