Medium 6.5Published Oct 8, 2026

CVE-2026-107290Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch`

Updated under an hour ago (Oct 28, 2026, 2:23 AM ET)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for pydantic-ai

Exploited in the last 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 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.

CVSS: 6.5 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): CWE-1333
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Analyzed
Record last updated: Oct 9, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

pydantic pydantic-ai pydantic:ai (from the name)	from 1.77.0, < 1.107.6; from 2.0.0b1, < 2.44.0	CNA record
pydantic pydantic-ai-slim pydantic:ai_slim (from the name)	from 1.77.0, < 1.107.6; from 2.0.0b1, < 2.44.0	CNA record
pydantic pydantic_ai pydantic:pydantic_ai	from 1.77.0 before 1.107.6; from 2.0.0 before 2.44.0	NVD

References

References

https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-fpf4-vwcp-v4hp	x-refsource-confirm, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/8397	x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/8399	x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/8418	x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/pull/84332	x-refsource-misc, broken-link
https://github.com/pydantic/pydantic-ai/pull/8434	x-refsource-misc, patch, vendor-advisory
https://github.com/pydantic/pydantic-ai/commit/2faa6181d8a17d83bc9516d035c5270db8730fa0	x-refsource-misc, patch
https://github.com/pydantic/pydantic-ai/commit/9cdc952e4c3319e85a3e04f2de49fbbb765bd38b	x-refsource-misc, patch
https://github.com/pydantic/pydantic-ai/commit/a93ea5226be1e93ae13131ae3f22287190411389	x-refsource-misc, patch
https://github.com/pydantic/pydantic-ai/commit/c3fd1cc1f15fdbf750d78e4e3ec1e8b4d6a3d920	x-refsource-misc, exploit, patch
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The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.