CVE-2026-256407.1HighCWE-22

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

pydantic · pydantic-ai

Affected: pydantic-ai · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.4%probability of exploitation in the next 30 days

31st percentile

050100

Higher than 31% of scored CVEs

7.1HighCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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 products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

pydantic · pydantic-ai>= 1.34.0, < 1.51.0

On the Atlas

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Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Path Traversal · File and Path Handling
Vendor: pydantic
Published: February 2026
Band: Unlikely (under 1%), February 2026

CoverageNo articles yet

No CyberSIXT article names CVE-2026-25640 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.