Vulnerability in Pydantic Pydantic-Ai
CVE-2026-107290
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.
Vulnerability class: ReDoS (Regular Expression Denial of Service)
Published .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Pydantic Pydantic-Ai — versions >= 1.77.0, < 1.107.6, >= 2.0.0b1, < 2.44.0
- Pydantic Pydantic-Ai-Slim — versions >= 1.77.0, < 1.107.6, >= 2.0.0b1, < 2.44.0
Weakness classification (CWE)
References
- github.com/pydantic/pydantic-ai/security/advisories/GHSA-fpf4-vwcp-v4hp
- github.com/pydantic/pydantic-ai/pull/8397
- github.com/pydantic/pydantic-ai/pull/8399
- github.com/pydantic/pydantic-ai/pull/8418
- github.com/pydantic/pydantic-ai/pull/84332
- github.com/pydantic/pydantic-ai/pull/8434
- github.com/pydantic/pydantic-ai/commit/2faa6181d8a17d83bc9516d035c5270db8730fa0
- github.com/pydantic/pydantic-ai/commit/9cdc952e4c3319e85a3e04f2de49fbbb765bd38b
- github.com/pydantic/pydantic-ai/commit/a93ea5226be1e93ae13131ae3f22287190411389
- github.com/pydantic/pydantic-ai/commit/c3fd1cc1f15fdbf750d78e4e3ec1e8b4d6a3d920
Frequently asked questions
- What is CVE-2026-107290?
- CVE-2026-107290 is a medium-severity vulnerability in Pydantic Pydantic-Ai, classified under Inefficient Regular Expression Complexity. CVSS score: 6.5/10. Published 2026-10-08.
- How severe is CVE-2026-107290?
- Medium severity. CVSS v3 base score is 6.5 out of 10.