GHSA-49h3-cwhj-4737

Summary

Cloudreve's WOPI PUT_RELATIVE handler treats X-WOPI-SuggestedTarget as a path, not a filename. It splits the header on / and joins the segments onto the source file's directory with URI.JoinRaw, which feeds Go's url.JoinPath. url.JoinPath resolves ./.. segments, so a slash-bearing target such as a/../../evil.docx collapses to a location outside the source file's directory. The lower-level upload path then validates only the final, already-cleaned basename (evil.docx), which is harmless, and checks ownership against the resolved ancestor — which is still the same user's drive.

A WOPI access token is bound to exactly one file (the route enforces fileId == session.FileID with a 403 otherwise). PUT_RELATIVE escapes that per-file scope: a token issued for one file can create (and, conditionally, overwrite) files elsewhere in the same account.

Root cause (verified at 26b6b10)

1. Token is single-file scoped (the boundary being escaped) — middleware ViewerSessionValidation:

fileId := hashid.FromContext(c)
if fileId != session.FileID {           // 403 — token is bound to ONE file
    c.Status(http.StatusForbidden); c.Abort(); return
}

Route: wopi := noAuth.Group("file/wopi", middleware.HashID(hashid.FileID), middleware.ViewerSessionValidation()); wopi.POST(":id", controllers.ModifyFile) → POST /api/v4/file/wopi/:id?access_token=<token>.

2. PUT_RELATIVE dispatch — routers/controllers/wopi.go:

case wopi.MethodPutRelative:            // X-WOPI-Override: PUT_RELATIVE
    err = service.PutContent(c, true)

3. SuggestedTarget joined as a path — service/explorer/viewer.go:

fileName, _ := wopi.UTF7Decode(c.GetHeader(wopi.SuggestedTargetHeader)) // X-WOPI-SuggestedTarget
fileUriParsed, _ := fs.NewUriFromString(fileUri)
if strings.HasPrefix(fileName, ".") { /* treat as extension */ }
fileUri = fileUriParsed.DirUri().JoinRaw(fileName).String()             // <-- path...