Description
Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy fetches metadata for user-supplied post URLs and, under the default StoreLinkPreviews image mode, downloads the preview image through local pict-rs. While the top-level page URL is checked against internal IP ranges, the extracted og:image URL is not subject to the same restriction. As a result, an authenticated low-privileged user can submit an attacker-controlled public page whose Open Graph image points to an internal image endpoint. Lemmy will fetch that internal image server-side and store a local thumbnail that can then be served back to users. This issue has been patched in version 0.19.18.
Problem types
CWE-918: Server-Side Request Forgery (SSRF)
Product status
References
github.com/.../lemmy/security/advisories/GHSA-h6hf-9846-xwrq
github.com/LemmyNet/lemmy/releases/tag/0.19.18