7.1

CVSS Score

3.1

-

CVSS Score

Basic Information

Concerned about an active attack path?

Talk to our security experts and see Miggo in action.

Miggo Vulnerability Database

→

CVE-2026-25640

CVE-2026-25640: Pydantic AI affected by Stored XSS via Path Traversal in Web UI CDN URL

Pydantic AI is a Python agent framework for building applications and workflows with Generative AI. From 1.34.0 to before 1.51.0, a path traversal vulnerability in the Pydantic AI web UI allows an attacker to serve arbitrary JavaScript in the context of the application by crafting a malicious URL. In affected versions, the CDN URL is constructed using a version query parameter from the request URL. This parameter is not validated, allowing path traversal sequences that cause the server to fetch and serve attacker-controlled HTML/JavaScript from an arbitrary source on the same CDN, instead of the legitimate chat UI package. If a victim clicks the link or visits it via an iframe, attacker-controlled code executes in their browser, enabling theft of chat history and other client-side data. This vulnerability only affects applications that use Agent.to_web to serve a chat interface and clai web to serve a chat interface from the CLI. These are typically run locally (on localhost), but may also be deployed on a remote server. This vulnerability is fixed in 1.51.0.

(GitHub Advisory)

Miggo Vulnerability Database

→

CVE-2026-25640

CVE-2026-25640:

7.1

CVSS Score

3.1

-

CVSS Score

Basic Information

Is this CVE running in your environment?

Easily map the attack path and prioritize which CVEs are a threat to your organization

Validate Exposure

Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
pydantic-ai	pip	>= 1.34.0, < 1.51.0	1.51.0
pydantic-ai-slim	pip	>= 1.34.0, < 1.51.0	1.51.0

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability is a path traversal flaw in the Pydantic AI web UI, leading to Cross-Site Scripting (XSS). The root cause lies in the create_web_app function, specifically its inner index request handler. This handler unsafely reads a version parameter from the URL's query string. This untrusted version is then passed to the _get_ui_html function, which uses it to construct a URL to fetch the UI's HTML from a CDN. Because the version parameter is not sanitized for path traversal characters (like ../), an attacker can craft a malicious URL that tricks the server into fetching and serving arbitrary HTML/JavaScript from the CDN's host instead of the legitimate chat UI. The vulnerability is exposed in applications that use either the Agent.to_web method or the clai web command-line tool, as both are entry points that create the vulnerable web application. The patch remediates this by completely removing the logic that reads the version from the query parameters and instead hardcoding the CDN URL, while providing a new, safe html_source parameter for developers to customize the UI source in their application code.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

Vulnerability Intelligence
Miggo AI

Unlock WAF rules for this CVE

Generate vendor-ready rules for the observed attack patterns, plus reasoning and safe deployment guidance

Get WAF rules

WAF Protection Rules

WAF Rule

W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.W** rul*s *v*il**l* *or Mi**o *ustom*rs only.

Reasoning

*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.