CVE-2026-55497: Cloudreve: Denial of Service - Image decompression / pixel bomb in thumbnail & avatar decoding crashes the server

Cloudreve’s built-in image processor decodes user-supplied images with Go’s standard-library decoders (image/png, image/jpeg, image/gif) and guards only the compressed file size — never the decoded pixel dimensions. Go’s decoders allocate a pixel buffer sized bytesPerPixel × width × height taken straight from the image header (e.g. a PNG’s IHDR), with no upper bound on width/height. A tiny (tens-of-bytes) image that declares enormous dimensions therefore forces a multi-gigabyte-to-terabyte allocation (make([]uint8, …)), exhausting memory. The resulting out-of-memory condition is a fatal Go runtime error / kernel OOM-kill that recover() cannot catch, terminating the whole Cloudreve process for all users.

Two reachable sinks share the same root cause:

1. Avatar upload (PUT /api/v4/user/setting/avatar) — decodes synchronously in the request handler. Any authenticated user. Cleanest single-request PoC.
2. Thumbnail generation (built-in generator, enabled by default) — decodes in the thumbnail queue worker. Reachable for the user’s own files and for files inside a share, so a planted bomb can be (re)triggered through a public share link.

Post-auth, low privilege. A single 65-byte upload deterministically takes the instance offline.