Cloudreve: Privilege Scope Bypass: State-Mutating Admin Operations Accessible via Read-Only OAuth Scope

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No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

22 Sep 2026 15:30:59 UTC

Source modified

22 Sep 2026 17:43:54 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 3.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N

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.

Source published

Sep 22, 2026, 3:30:59 PM (timezone not stated)

Source modified

Sep 22, 2026, 5:43:54 PM (timezone not stated)

Observed here

11 Nov 2026 16:09:16 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 3.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N

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.

Source published

22 Sep 2026 16:17:55 UTC

Source modified

22 Sep 2026 18:17:19 UTC

Observed here

25 Oct 2026 16:19:04 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 3.8 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N

### Summary There is a privilege scope bypass in Cloudreve's admin API where two endpoints that mutate server state are missing the write-scope enforcement that their neighboring endpoints correctly apply. Specifically, the WOPI configuration fetch endpoint and the SMTP test/mail endpoint can both be triggered by an OAuth token that only has Admin.Read authorization — no Admin.Write needed. This breaks the intended OAuth scope boundary in a way that's subtle enough to have slipped through but meaningful enough to matter in a real deployment. ### Details The root cause is an inconsistency in how the admin tool routes are wired up in `routers/router.go`. The admin route group sets a baseline of `ScopeAdminRead` for everything underneath it (around line 868), and most write-capable endpoints inside the `tool` sub-group correctly layer on an additional `RequiredScopes(types.ScopeAdminWrite)` check on top of that. For example, the thumbnail executable setter (line 929) and the entity URL cache deletion (line 937) both do this properly. The two endpoints that don't follow this pattern are `tool.GET('wopi')` (line 925) and `tool.POST('mail')` (line 933). Despite `POST /mail` clearly triggering an outbound email and `GET /wopi` fetching or probing WOPI service connectivity, neither has the `ScopeAdminWrite` guard. What that means in practice is that any OAuth application granted only Admin.Read — a scope that should be limited to inspecting configuration, not changing anything — can silently invoke both of these operations. The developer looking at the route definitions would reasonably assume all the write-adjacent tool endpoints were protected, because the ones right above and below them are. It's the kind of gap that's easy to miss in a code review. ### PoC ```bash # OAuth app with ONLY Admin.Read scope can send emails: curl -s -X POST -H 'Content-Type: application/json' \ -H 'Authorization: Bearer <ADMIN_READ_ONLY_TOKEN>' \ 'https://cloudreve.example.com/api/v4/admin/tool/mail' \ -d '{"settings":{"smtpHost":"smtp.gmail.com","smtpPort":"587",...},"to":"[email protected]"}' # Expected: 403 Forbidden (if Admin.Write was required) # Actual: 200 OK, email is sent ``` ### Impact An OAuth application or API key scoped to Admin.Read can send arbitrary emails through the server's configured SMTP account and probe internal WOPI service endpoints — both actions that should require elevated write authorization. In multi-party deployments where Admin.Read tokens are issued more liberally (e.g., to monitoring integrations or third-party plugins), a compromised or malicious token holder gains capabilities well beyond what the scope contract implies. Scope separation in OAuth 2.0 is a security boundary, not just a convention, and its violation here could factor into broader attack chains. ### Fix Add `middleware.RequiredScopes(types.ScopeAdminWrite)` as the first handler argument to both the `tool.GET('wopi')` and `tool.POST('mail')` route definitions in `routers/router.go`. This brings them in line with `tool.POST('thumbExecutable')` at line 929 and `tool.DELETE('entityUrlCache')` at line 937, which already follow the correct pattern. No logic changes are needed — it's purely an additive middleware insertion. **If possible, please apply for a CVE number when publishing. I would greatly appreciate it.**

Source published

22 Sep 2026 20:40:35 UTC

Source modified

1 Oct 2026 20:56:21 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N

Publisher rating · LOW

Cloudreve: Privilege Scope Bypass: State-Mutating Admin Operations Accessible via Read-Only OAuth Scope in github.com/cloudreve/Cloudreve

Source published

1 Oct 2026 20:23:38 UTC

Source modified

1 Oct 2026 20:45:14 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.