CVE-2026-107290: CWE-1333: Inefficient Regular Expression Complexity in pydantic pydantic-ai
Description
CVE-2026-107290 is a vulnerability in pydantic-ai, a Python agent framework for Generative AI applications. Versions from 1.77.0 up to but not including 1.107.6, and from 2.0.0b1 up to but not including 2.44.0, contain inefficient regular expression processing in the local web_fetch_tool and WebFetch local fallback. This inefficiency can cause the event loop to stall when processing attacker-controlled pages, leading to denial of service conditions. The issue is resolved in versions 1.107.6 and 2.44.0.
CVSS v3.1
Score 6.5medium
Affected software
pydantic
pydantic-ai
pydantic
pydantic-ai-slim
pkg:pypi/pydantic-aiRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability involves quadratic complexity in regular expression operations related to title extraction, whitespace normalization, and ordered-list numbering within pydantic-ai's local web_fetch_tool and WebFetch fallback. An attacker can supply crafted content that causes prolonged blocking of the event loop, stalling other agent runs and requests. Additionally, unsupported codecs or deeply nested HTML/JSON can abort individual runs. This denial of service risk affects versions >=1.77.0 <1.107.6 and >=2.0.0b1 <2.44.0 and is fixed in 1.107.6 and 2.44.0.
Potential Impact
The vulnerability results in denial of service by blocking the event loop for extended periods, which stalls other agent operations and requests. It does not impact confidentiality or integrity but can significantly degrade availability of the affected pydantic-ai agents.
Mitigation Recommendations
This issue is fixed in pydantic-ai versions 1.107.6 and 2.44.0. Users should upgrade to these versions or later to remediate the vulnerability. No other mitigation steps are indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-10-07T15:53:23.586Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ac7c7552cdf04f65629ffff
Added to database: 10/08/2026, 16:39:49 UTC
Last enriched: 10/08/2026, 16:49:00 UTC
Last updated: 10/08/2026, 17:36:25 UTC
Views: 8
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.