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.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
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 | 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.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-77637 being exploited?
There is no known exploitation of CVE-2026-77637 in the wild and no public exploit code.
Sources
Also known as GHSA-w89x-c962-c44g, GO-2026-6576.