# CVE-2026-77637: Cloudreve privilege scope bypass in admin API endpoints

Source: https://junglewise.ai/threats/cve-2026-77637-cloudreve-privilege-scope-bypass-in-admin-api-endpoints  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77637 · Severity: low · CVSS 3.8 · Published 2026-09-22

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.

Technologies: [Cloudreve](https://junglewise.ai/threats/technologies/cloudreve), [github.com/cloudreve/Cloudreve (Go)](https://junglewise.ai/threats/technologies/github-com-cloudreve-cloudreve), [github.com/cloudreve/Cloudreve/v3 (Go)](https://junglewise.ai/threats/technologies/github-com-cloudreve-cloudreve-v3), [github.com/cloudreve/Cloudreve/v4 (Go)](https://junglewise.ai/threats/technologies/github-com-cloudreve-cloudreve-v4). Vendors: [Cloudreve](https://junglewise.ai/threats/vendors/cloudreve), [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-77637 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77637 being exploited in the wild.

**How severe is CVE-2026-77637?** Low severity, with a CVSS score of 3.8, published 22 September 2026.

**Which products and versions are affected?** Cloudreve <UNKNOWN>; github.com/cloudreve/Cloudreve (Go) SEMVER:introduced=0; github.com/cloudreve/Cloudreve/v3 (Go) SEMVER:introduced=0; github.com/cloudreve/Cloudreve/v4 (Go) < 4.0.0-20260715070110-bce08f88e9d8, SEMVER:introduced=0,fixed=4.0.0-20260715070110-bce08f88e9d8.

**Is there a fix for CVE-2026-77637?** Yes. github.com/cloudreve/Cloudreve/v4 (Go): upgrade to 4.0.0-20260715070110-bce08f88e9d8 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77637 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-77637?** Check whether you run Cloudreve, github.com/cloudreve/Cloudreve (Go), github.com/cloudreve/Cloudreve/v3 (Go) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/cloudreve/Cloudreve/v4 (Go): upgrade to 4.0.0-20260715070110-bce08f88e9d8 or later

  ```sh
  go get github.com/cloudreve/Cloudreve/v4@v4.0.0-20260715070110-bce08f88e9d8
  ```


## 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>

## Identifiers

- CVE-2026-77637
- GHSA-w89x-c962-c44g
- GO-2026-6576

## Timeline

- 2026-09-22: disclosed
- other: CVE-2026-77637 assigned

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