CVE-2026-53580 affects Trilium, an open-source hierarchical note-taking application, in versions prior to 0.104.0. The vulnerability stems from the automatic image-download feature accepting file:// URLs without path validation, allowing authenticated users to read arbitrary local files accessible by the Trilium process. When a note is saved, Trilium fetches image sources including file:// URIs, storing file contents as note attachments retrievable by the attacker. Additionally, pointing the feature at unbounded sources like /dev/zero triggers uncontrolled memory allocation, causing a server crash (DoS). The vulnerability is enabled by default and reachable via the web UI, ETAPI, web clipper, and note imports, requiring only a valid authenticated session or ETAPI token. The issue has been fixed in version 0.104.0.