Bug 2437753 (CVE-2026-25640)

Summary: CVE-2026-25640 Pydantic AI: Pydantic AI: Arbitrary code execution and information disclosure via path traversal in web UI
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: bbrownin
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Pydantic AI. A remote attacker can exploit a path traversal vulnerability in the Pydantic AI web UI by crafting a malicious URL. This vulnerability arises from insufficient validation of the version query parameter, allowing the server to fetch and serve attacker-controlled HTML or JavaScript. If a victim clicks on such a link, malicious code can execute in their browser, potentially leading to the theft of sensitive client-side data, including chat history.
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Description OSIDB Bzimport 2026-02-09 11:04:09 UTC 
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.