Cloudreve up to 4.17.x Routing Middleware routers/router.go tool.GET/tool.POST improper authorization

Summaryinfo

A vulnerability, which was classified as critical, was found in Cloudreve up to 4.17.x. Affected by this issue is the function tool.GET/tool.POST of the file routers/router.go of the component Routing Middleware. Executing a manipulation can lead to improper authorization. This vulnerability appears as CVE-2026-77637. The attack may be performed from remote. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Cloudreve up to 4.17.x. It has been declared as critical. This vulnerability affects the function tool.GET/tool.POST of the file routers/router.go of the component Routing Middleware. The manipulation with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-77637 since 08/20/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1548.002.

Upgrading to version 4.18.0 eliminates this vulnerability.

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Productinfo

Type

• Cloud Software

Name

• Cloudreve

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17

Website

• Product: https://github.com/cloudreve/cloudreve/

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