CVE-2026-77637

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, PrepareUpload checks a stale in-memory user storage value and later applies an unconditional storage charge outside the same quota-enforcing transaction. An authenticated user with Files.Write permission can issue concurrent upload-session requests that read the same capacity snapshot, all pass the MaxStorage check, and reserve their declared sizes through CommitWithStorageDiff, exceeding the account quota and exhausting host storage.

In Cloudreve prior to 4.18.0, the ValidateExternalURL server-side request forgery (SSRF) guard in pkg/request/ssrf.go passes resolved addresses to checkIP without decoding NAT64, IPv4-compatible, and 6to4 IPv4-in-IPv6 transition forms. An authenticated user with remote-download access can provide SrcUri through RemoteDownloadTask.createDownloadTask so a wrapper embedding a loopback, private, link-local, or cloud metadata IPv4 address is classified as public and fetched, exposing internal service responses and cloud instance credentials. IPv4-mapped IPv6 addresses remain blocked because Go converts that form with net.IP.To4.

In Cloudreve before version 4.17.0, WOPI session validation uses only the session-id prefix of the access token and does not enforce the requested action, allowing a malicious viewer to forge the token suffix and invoke file write operations.

Vulnerability in Cloudreve before 4.17.0, where the POST /api/v4/admin/policy/oauth/signin endpoint requires only Admin.Read permission but allows modification of OneDrive storage policy credentials without Admin.Write, enabling changes to secret and app_id.

In Cloudreve before version 4.17.0, a single-file share event-stream subscription resolves the share root to the owner's parent folder and subscribes to it, allowing an authenticated share recipient to receive information about unshared sibling files and folders.

Cloudreve before version 4.17.0 has a vulnerability in thumbnail and avatar decoders that limit compressed file size but not decoded pixel dimensions. An authenticated user can submit a small PNG, JPEG, or GIF that triggers unbounded memory allocation and terminates the Cloudreve process due to an out-of-memory error.

Cloudreve before version 4.17.0 has a vulnerability in the GET /api/v4/user/search endpoint that calls SearchActive without adding a StatusActive predicate and serializes matches at RedactLevelUser. This allows any logged-in user to enumerate email addresses and profile metadata for inactive or banned accounts.

Cloudreve before version 4.17.0 has a vulnerability in the WOPI PUT_RELATIVE handler that passes X-WOPI-SuggestedTarget to URI.JoinRaw as a path rather than a filename. This allows slash and dot-dot segments to escape the source file directory and create or conditionally overwrite files elsewhere in the same owner account.

In Cloudreve prior to version 4.16.1, a WebDAV account scoped to a configured folder can bypass the restriction by sending paths containing encoded ".." characters (e.g., %2e%2e). The stripPrefix function in pkg/webdav/webdav.go joins the decoded request suffix to the account root without checking containment, allowing reading and listing files outside the folder, and for writable accounts also creating, overwriting, moving, or deleting them.

Cloudreve before version 4.16.1 allows non-admin users with remote download permission to fetch internal-only URLs (e.g., localhost, loopback) via the POST /api/v4/workflow/download endpoint. The vulnerability is due to missing blocking of loopback, localhost, IPv6 localhost, and redirect-to-loopback targets.