CVE-2026-107290: Pydantic AI: Event loop blocked by quadratic title extraction in `web_fetch`
Vulnerability summary
CVE-2026-107290 is a medium (CVSS 6.5) vulnerability in pydantic pydantic_ai. EPSS estimates a 0.51% chance of exploitation in the next 30 days, higher than 43.7% of scored vulnerabilities. 1 public exploit is recorded.
Not severe (CVSS 6.5, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Timeline
- 08-10-2026PublishedVulnerability first disclosed.
- 09-10-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
3 scores · 3 sources · 1 version- OSV · PypiEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.51%
Chance of exploitation in the next 30 days
Percentile
44%
Versus all other CVEs
30-day change
Change unavailable
Change unavailable
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
1 foundPydantic Ai
Maturity: poc
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Pydantic3 products
- pydantic_ai≥ 1.77.0, < 1.107.6 | ≥ 2.0.0, < 2.44.0
- pydantic-ai≥ 1.77.0, < 1.107.6 | ≥ 2.0.0b1, < 2.44.0
- pydantic-ai-slim≥ 1.77.0, < 1.107.6 | ≥ 2.0.0b1, < 2.44.0
PyPI2 products
- pydantic-ai≥ 1.77.0, < 1.107.6 | ≥ 2.0.0b1, < 2.44.0
- pydantic-ai-slim≥ 1.77.0, < 1.107.6 | ≥ 2.0.0b1, < 2.44.0
2 vendors · 5 products
References
19 links- github.com/pydantic/pydantic-ai/security/advisories/GHSA-fpf4-vwcp-v4hpX Refsource CONFIRMWEBVendor Advisory
- github.com/pydantic/pydantic-ai/commit/2faa6181d8a17d83bc9516d035c5270db8730fa0X Refsource MISCWEBPatch
- github.com/pydantic/pydantic-ai/commit/9cdc952e4c3319e85a3e04f2de49fbbb765bd38bX Refsource MISCWEBPatch
- github.com/pydantic/pydantic-ai/commit/a93ea5226be1e93ae13131ae3f22287190411389X Refsource MISCWEBPatch
- github.com/pydantic/pydantic-ai/commit/c3fd1cc1f15fdbf750d78e4e3ec1e8b4d6a3d920X Refsource MISCWEBExploitPatch
Show all 19 references
- github.com/pydantic/pydantic-ai/commit/fb92ccfc3ca2735dab877e2ed73856681bf72ad1X Refsource MISCWEBPatch
- github.com/pydantic/pydantic-ai/releases/tag/v1.107.6X Refsource MISCWEBPatchRelease NotesVendor Advisory
- github.com/pydantic/pydantic-ai/releases/tag/v2.44.0X Refsource MISCWEBPatchRelease NotesVendor Advisory
- pypi.org/project/pydantic-aiPACKAGE
