CVE-2026-107287: pydantic ai DoS — Fix

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.

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CVSS v3.1 Score

6.5

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

CWE-407 CWE-407

Affected Products

Vendor	Product	Versions
pydantic	pydantic_ai	1.77.0 — 1.107.7
pydantic	pydantic_ai	2.0.0 — 2.52.0

References

Advisories & Patches

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

Frequently Asked Questions

What is CVE-2026-107287? +

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. It has a CVSS v3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-107287? +

CVE-2026-107287 has a CVSS v3.1 score of 6.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-107287? +

CVE-2026-107287 affects products from pydantic, specifically: pydantic_ai. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-107287? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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