---
id: CVE-2026-25640
title: >-
  Pydantic AI is a Python agent framework for building applications and
  workflows with Generative AI
summary: >-
  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 …
severity: high
cvss: 7.1
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N'
cwe:
  - CWE-22
  - CWE-79
  - CWE-22
vendor: pydantic
product: pydantic_ai
affected:
  - 'pydantic_ai >= 1.34.0, < 1.51.0'
patched:
  - pydantic_ai 1.51.0
published: '2026-02-06'
updated: '2026-06-30'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-25640'
references:
  - url: 'https://github.com/pydantic/pydantic-ai/releases/tag/v1.51.0'
    label: security-advisories@github.com
  - url: >-
      https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-wjp5-868j-wqv7
    label: security-advisories@github.com
  - url: 'https://access.redhat.com/security/cve/CVE-2026-25640'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2437753'
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25640.json
    label: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
tags:
  - nvd
epss: 0.00336
epssPercentile: 0.27136
ingestedAt: '2026-07-03T18:53:52.175Z'
---

## Overview

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.

## Affected

- `pydantic_ai >= 1.34.0, < 1.51.0`

## Remediation

Upgrade past the affected range:

- `pydantic_ai 1.51.0`