{"id":"CVE-2026-25640","aliases":["GHSA-wjp5-868j-wqv7","PYSEC-2026-2979","PYSEC-2026-2983"],"url":"https://o3.security/vulnerability/CVE-2026-25640","summary":"Pydantic AI affected by Stored XSS via Path Traversal in Web UI CDN URL","details":"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.","published":"2026-02-06T20:01:53.892Z","modified":"2026-08-07T11:50:38.440731674Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"pydantic-ai","fixedVersion":"1.51.0"},{"ecosystem":"PyPI","name":"pydantic-ai-slim","fixedVersion":"1.51.0"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/pydantic/pydantic-ai/releases/tag/v1.51.0"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25640.json"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-25640"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/25xxx/CVE-2026-25640.json"},{"type":"ADVISORY","url":"https://github.com/pydantic/pydantic-ai/security/advisories/GHSA-wjp5-868j-wqv7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-25640"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2437753"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T11:50:38.440731674Z"}}