TheLibrarian.io Internal Cloud Environment Access via web_fetch Tool

Affected Vendor(s)

Affected Product(s)

Summary

The web_fetch tool is intended to accept a public URL and retrieve the contents. When asked to retrieve the contents from a private destination (such as http://localhost), the AI rightly refuses. Unfortunately, it can be easily tricked and subverted.

‍By providing encoded or non-obvious variations, the AI does not validate the input and proceeds to point its fetching client inward, thereby exposing internal information.

Timeline

Discovered on
October 8, 2025
Disclosed to Vendor on
October 10, 2025
Published on
December 17, 2025

Credit

Blog Post

References

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