Security: Unbounded limit parameter in user search can be abused for resource exhaustion

[tomaioo]

Summary

Security: Unbounded limit parameter in user search can be abused for resource exhaustion

Problem

Severity: Medium | File: lib/Controller/UserApiController.php:L39

The index(string $filter = '', int $limit = 5) method accepts client-controlled limit and passes it directly to collaborator search. Without an upper bound, an attacker can request very large limits, causing expensive directory lookups and increased response size.

Solution

Enforce a strict maximum (e.g., 10-50) for limit before invoking search, and consider server-side rate limiting for this endpoint.

Changes

• lib/Controller/UserApiController.php (modified)

[github-actions]

Hello there,
Thank you so much for taking the time and effort to create a pull request to our Nextcloud project.

We hope that the review process is going smooth and is helpful for you. We want to ensure your pull request is reviewed to your satisfaction. If you have a moment, our community management team would very much appreciate your feedback on your experience with this PR review process.

Your feedback is valuable to us as we continuously strive to improve our community developer experience. Please take a moment to complete our short survey by clicking on the following link: https://cloud.nextcloud.com/apps/forms/s/i9Ago4EQRZ7TWxjfmeEpPkf6

Thank you for contributing to Nextcloud and we hope to hear from you soon!

(If you believe you should not receive this message, you can add yourself to the blocklist.)

[mejo-]

Thanks @tomaioo 🙏

[mejo-]

/backport to stable33

[mejo-]

/backport to stable32