# CVE-2026-77637: Cloudreve: Privilege Scope Bypass: State-Mutating Admin Operations Accessible via Read-Only OAuth Scope

> Attackers with read-only OAuth tokens can perform state-changing admin actions like sending emails or probing WOPI endpoints in Cloudreve.

- **Severity:** Low 3.8 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Sep 2026
- **Updated:** 22 Sep 2026
- **Also known as:** GHSA-w89x-c962-c44g, GO-2026-6576

## What is CVE-2026-77637?

CVE-2026-77637 is a low-severity missing authorization vulnerability in cloudreve, published on 22 Sep 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, tool.GET("wopi") and tool.POST("mail") in routers/router.go inherit ScopeAdminRead but omit the RequiredScopes(types.ScopeAdminWrite) middleware applied to neighboring state-changing admin tool routes. An OAuth application or API key limited to Admin.Read can therefore probe configured WOPI service endpoints and send arbitrary test email through the server SMTP configuration, exceeding the token's intended read-only authorization boundary. This issue is fixed in version 4.18.0.

Weakness: CWE-862 (Missing Authorization)

## Which versions are affected by CVE-2026-77637?

5 open source packages ship an affected version, including github.com/cloudreve/Cloudreve/v4, github.com/cloudreve/Cloudreve and github.com/cloudreve/Cloudreve/v3.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/cloudreve/Cloudreve/v4` | Go | All versions | 4.0.0-20260715070110-bce08f88e9d8 |
| `github.com/cloudreve/Cloudreve/v4` | Go | All versions | 4.0.0-20260715070110-bce08f88e9d8 |
| `github.com/cloudreve/Cloudreve/v4` | Go | All versions | 4.0.0-20260715070110-bce08f88e9d8 |
| `github.com/cloudreve/Cloudreve` | Go | All versions | None |
| `github.com/cloudreve/Cloudreve/v3` | Go | All versions | None |

## How do I fix CVE-2026-77637?

Upgrade github.com/cloudreve/Cloudreve/v4 to 4.0.0-20260715070110-bce08f88e9d8 or later.

## Is CVE-2026-77637 being exploited?

There is no known exploitation of CVE-2026-77637 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77637 and fix it if it is affected.

What it is: CVE-2026-77637 is a low-severity missing authorization vulnerability in cloudreve, published on 22 Sep 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-77637 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/cloudreve/Cloudreve/v4 (Go): affected all versions; fixed in 4.0.0-20260715070110-bce08f88e9d8
- github.com/cloudreve/Cloudreve/v4 (Go): affected all versions; fixed in 4.0.0-20260715070110-bce08f88e9d8
- github.com/cloudreve/Cloudreve/v4 (Go): affected all versions; fixed in 4.0.0-20260715070110-bce08f88e9d8
- github.com/cloudreve/Cloudreve (Go): affected all versions; no fix listed
- github.com/cloudreve/Cloudreve/v3 (Go): affected all versions; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-77637/ (Markdown: https://insights.sbomify.com/CVE-2026-77637/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77637
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77637
- OSV: https://osv.dev/vulnerability/CVE-2026-77637

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77637/
Summaries are generated and may contain mistakes; the official description above is the record.