Executive brief
Cloudreve is a file management system that uses OAuth 2.0 scopes to control what actions authorized applications can perform. Two admin endpoints that should require write authorization—one for sending emails via SMTP and another for probing WOPI service connectivity—can be triggered by applications with only read-level permissions. This scope boundary violation means a compromised or malicious read-only token could send arbitrary emails or probe internal services, actions that should be restricted to administrators.
Technical details
The vulnerability is a privilege scope bypass in Cloudreve's admin API routing layer (`routers/router.go`). The root cause is inconsistent OAuth scope enforcement: while most write-capable endpoints under the admin tool route group correctly layer on an additional `RequiredScopes(types.ScopeAdminWrite)` middleware check on top of the baseline `ScopeAdminRead`, two endpoints—`GET /api/v4/admin/tool/wopi` and `POST /api/v4/admin/tool/mail`—omit this check. This allows any OAuth token with only Admin.Read scope to invoke state-mutating operations (sending emails via SMTP, probing WOPI service connectivity) that should require Admin.Write scope. No user interaction or additional authentication is required; network access to the API is sufficient. The fix is straightforward: add the missing `RequiredScopes(types.ScopeAdminWrite)` middleware to both endpoints, as is done correctly for neighboring endpoints like the thumbnail executable setter and entity URL cache deletion.
Affected products
- Cloudreve Cloudreve <UNKNOWN>
Timeline
- 2026-09-22: disclosed
- other: CVE-2026-77637 assigned