Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch` (pydantic pydantic-ai)
At a glance
- Source
- NVD
- EPSS
- EPSS 0.51 % · percentile 44 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Analyzed
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.
Weaknesses (CWE)
- CWE-1333 — Inefficient Regular Expression Complexity
References
- https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-fpf4-vwcp-v4hp
- https://github.com/pydantic/pydantic-ai/pull/8397
- https://github.com/pydantic/pydantic-ai/pull/8399
- https://github.com/pydantic/pydantic-ai/pull/8418
- https://github.com/pydantic/pydantic-ai/pull/84332
- https://github.com/pydantic/pydantic-ai/pull/8434
- https://github.com/pydantic/pydantic-ai/commit/2faa6181d8a17d83bc9516d035c5270db8730fa0
- https://github.com/pydantic/pydantic-ai/commit/9cdc952e4c3319e85a3e04f2de49fbbb765bd38b
- https://github.com/pydantic/pydantic-ai/commit/a93ea5226be1e93ae13131ae3f22287190411389
- https://github.com/pydantic/pydantic-ai/commit/c3fd1cc1f15fdbf750d78e4e3ec1e8b4d6a3d920
- https://github.com/pydantic/pydantic-ai/commit/fb92ccfc3ca2735dab877e2ed73856681bf72ad1
- https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.6
- https://github.com/pydantic/pydantic-ai/releases/tag/v2.44.0
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | MEDIUM 6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | GitHub_M |
| CVSS 3.1 | MEDIUM 6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H | NVD · security-advisories@github.com (Secondary) |
Advisories
- GHSA-fpf4-vwcp-v4hp — Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch`
- PYSEC-2026-4277 — Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch`
- PYSEC-2026-4286 — Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch`
European references
- ENISA EUVD · EUVD-2026-95093
- GCVE · GCVE-0-2026-107290
Affected configurations (NVD CPE)
cpe:2.3:a:pydantic:pydantic_ai:*:*:*:*:*:python:*:*≥ 1.77.0 < 1.107.6cpe:2.3:a:pydantic:pydantic_ai:*:-:*:*:*:python:*:*≥ 2.0.0 < 2.44.0
Affected products
| Product | Versions |
|---|---|
| pydantic · pydantic-ai | affected >= 1.77.0, < 1.107.6 ; affected >= 2.0.0b1, < 2.44.0 |
| pydantic · pydantic-ai-slim | affected >= 1.77.0, < 1.107.6 ; affected >= 2.0.0b1, < 2.44.0 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |