Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch`
Summary
| CVE | CVE-2026-107290 |
|---|---|
| State | PUBLISHED |
| Assigner | GitHub_M |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-10-08 17:17:14 UTC |
| Updated | 2026-10-08 17:17:14 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 6.5 MEDIUM from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Problem Types: CWE-1333 | CWE-1333 CWE-1333: Inefficient Regular Expression Complexity
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | DECLARED | 6.5 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Pydantic | Pydantic-ai | affected >= 1.77.0, < 1.107.6 | Not specified |
| CNA | Pydantic | Pydantic-ai | affected >= 2.0.0b1, < 2.44.0 | Not specified |
| CNA | Pydantic | Pydantic-ai-slim | affected >= 1.77.0, < 1.107.6 | Not specified |
| CNA | Pydantic | Pydantic-ai-slim | affected >= 2.0.0b1, < 2.44.0 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/pydantic/pydantic-ai/commit/c3fd1cc1f15fdbf750d78e4e3ec1e8b4d... | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/pull/8418 | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/pull/8399 | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/releases/tag/v2.44.0 | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/commit/a93ea5226be1e93ae13131ae3f2228719... | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/commit/fb92ccfc3ca2735dab877e2ed73856681... | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/pull/84332 | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/pull/8434 | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/commit/2faa6181d8a17d83bc9516d035c5270db... | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/releases/tag/v1.107.6 | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/commit/9cdc952e4c3319e85a3e04f2de49fbbb7... | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/pull/8397 | [email protected] | github.com | |
| github.com/pydantic/pydantic-ai/security/advisories/GHSA-fpf4-vwcp-v4hp | [email protected] | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.