CVE-2026-25640

Description

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.

References

Reference URLs as listed by NVD, grouped by a mechanical match on the link's host/pattern. Labels describe the link type only.

• Patch https://github.com/pydantic/pydantic-ai/releases/tag/v1.51.0
• Vendor advisory https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-wjp5-868j-wqv7
• Distro https://access.redhat.com/security/cve/CVE-2026-25640
• Distro https://bugzilla.redhat.com/show_bug.cgi?id=2437753
• Distro https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25640.json