Reference page — cumulative record through Monday, October 19, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-107290

CVE-2026-107290MEDIUM

Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch`

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   L   N  U  N  N  H    6.5   .0044   36.9     —

AFFECTED
  Product           Versions                Fixed
  pydantic-ai       >= 1.77.0, < 1.107.6 –  —
  pydantic-ai-slim  >= 1.77.0, < 1.107.6 –  —

TIMELINE
  Oct 7   Reserved by GitHub_M
  Oct 8   Published (CNA: GitHub_M)
  Oct 13  EXPLOIT PUBLISHED — CVE-2026-107290 (pydantic-ai). Public exploit reference added.

CWE-1333 · CNA: GitHub_M · CVSS v3.1 · 13 references · 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.

Lifecycle

Complete event history — 3 events, chronological
Date	Event	Detail
October 7, 2026	Reserved	Reserved by GitHub_M
October 8, 2026	Published	Published (CNA: GitHub_M)
October 13, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-107290 (pydantic-ai). Public exploit reference added.

Affected

Affected products and packages — 2 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
pydantic	pydantic-ai	—	>= 1.77.0, < 1.107.6	—
pydantic	pydantic-ai-slim	—	>= 1.77.0, < 1.107.6	—

Weaknesses

CWE-1333

References (13)

https://github.com/pydantic/pydantic-ai/commit/2faa6181d8a17d83bc9516d035c5270db8730fa0 [Patch]
https://github.com/pydantic/pydantic-ai/commit/9cdc952e4c3319e85a3e04f2de49fbbb765bd38b [Patch]
https://github.com/pydantic/pydantic-ai/commit/a93ea5226be1e93ae13131ae3f22287190411389 [Patch]
https://github.com/pydantic/pydantic-ai/commit/c3fd1cc1f15fdbf750d78e4e3ec1e8b4d6a3d920 [Exploit, Patch]
https://github.com/pydantic/pydantic-ai/commit/fb92ccfc3ca2735dab877e2ed73856681bf72ad1 [Patch]
https://github.com/pydantic/pydantic-ai/pull/8397 [Patch, Vendor Advisory]
https://github.com/pydantic/pydantic-ai/pull/8399 [Patch, Vendor Advisory]
https://github.com/pydantic/pydantic-ai/pull/8418 [Patch, Vendor Advisory]
https://github.com/pydantic/pydantic-ai/pull/84332 [Broken Link]
https://github.com/pydantic/pydantic-ai/pull/8434 [Patch, Vendor Advisory]
https://github.com/pydantic/pydantic-ai/releases/tag/v1.107.6 [Patch, Release Notes, Vendor Advisory]
https://github.com/pydantic/pydantic-ai/releases/tag/v2.44.0 [Patch, Release Notes, Vendor Advisory]
https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-fpf4-vwcp-v4hp [Vendor Advisory]

Authoritative record: CVE-2026-107290 at cve.org

Vendors: pydantic

Weaknesses: CWE-1333

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-107290 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Monday, October 19, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.