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Vulnerability · Published Oct 8, 2026 · Assigned by GitHub_M

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

Medium 6.5

In plain English

A medium-severity uncontrolled resource consumption in pydantic-ai from pydantic. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.5Medium
Exploit odds (30 days)0.3%top 79.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPIpydantic-ai1.107.7GHSA-v36g-jcw9-x7cw
PyPIpydantic-ai2.52.0GHSA-v36g-jcw9-x7cw
PyPIpydantic-ai1.107.7, 2.52.0PYSEC-2026-4281
PyPIpydantic-ai-slim1.107.7GHSA-v36g-jcw9-x7cw
PyPIpydantic-ai-slim2.52.0GHSA-v36g-jcw9-x7cw
PyPIpydantic-ai-slim1.107.7, 2.52.0PYSEC-2026-4290

Affected products (as reported)

VendorProductVersions
pydantic pydantic-ai >= 1.77.0, < 1.107.7>= 2.0.0b1, < 2.52.0
pydantic pydantic-ai-slim >= 1.77.0, < 1.107.7>= 2.0.0b1, < 2.52.0

Weakness: CWE-400, CWE-407 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

References