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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-77637: 0.33% estimated exploitation activity in the next 30 days; percentile 25.69 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

22 Sep 2026, 20:40 UTC

Last modified by the source

1 Oct 2026, 20:45 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-w89x-c962-c44g

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6576

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-w89x-c962-c44g

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-77637

Advisory: Cloudreve: Privilege Scope Bypass: State-Mutating Admin Operations Accessible via Read-Only OAuth Scope
IDs: CVE-2026-77637, GHSA-w89x-c962-c44g
Record: https://patchnext.com/advisories/cve-2026-77637 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/cloudreve/Cloudreve/v4 4.0.0-20260715070110-bce08f88e9d8. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/cloudreve/Cloudreve/v3: affected every version
- Go github.com/cloudreve/Cloudreve: affected every version
- Go github.com/cloudreve/Cloudreve/v4: affected < 4.0.0-20260715070110-bce08f88e9d8; fixed in 4.0.0-20260715070110-bce08f88e9d8

## Suggested inspection (read-only)
- Go github.com/cloudreve/Cloudreve/v3: check the installed version with your package manager.
- Go github.com/cloudreve/Cloudreve: check the installed version with your package manager.
- Go github.com/cloudreve/Cloudreve/v4: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/cloudreve/Cloudreve/v3, github.com/cloudreve/Cloudreve, github.com/cloudreve/Cloudreve/v4.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6576 (OSV record GO-2026-6576 lists affected ranges: Go github.com/cloudreve/Cloudreve >=0; Go github.com/cloudreve/Cloudreve/v3 >=0; Go github.com/cloudreve/Cloudreve/v4 >=0 <4.0.0-20260715070110-bce08f88e9d8 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-w89x-c962-c44g (OSV record GHSA-w89x-c962-c44g lists affected ranges: Go github.com/cloudreve/Cloudreve/v4 >=0 <4.0.0-20260715070110-bce08f88e9d8 (fixed))
- Verified: https://github.com/advisories/GHSA-w89x-c962-c44g (GitHub-reviewed advisory GHSA-w89x-c962-c44g lists affected ranges: Go github.com/cloudreve/Cloudreve/v4 >=0 <4.0.0-20260715070110-bce08f88e9d8)

Commands are suggestions: review each one before running it.