Attack Chain

1. An attacker compromises or obtains a low-privilege Ech0 admin account, such as one with only echo:read scope.
2. The attacker uses the compromised account to generate a new access token with limited scopes (e.g., echo:read).
3. The attacker crafts a request to /api/inbox using the low-scope access token in the Authorization header. Because this route lacks scope enforcement, the request succeeds despite the token's limited privileges.
4. The attacker crafts a request to /api/backup/export?token=<low_scope_admin_token> using the low-scope access token as the token parameter.
5. The /api/backup/export handler parses the token, extracts the user ID, and discards all other token metadata (scopes, audience, etc.).
6. The handler then rebuilds a new user context based only on the user ID, effectively elevating the low-scope token to full admin privileges.
7. The backup service executes, generating a ZIP archive containing sensitive data, including the application database and logs.
8. The attacker downloads the backup archive, gaining access to potentially sensitive information.

Impact

Successful exploitation allows attackers with limited admin access to escalate their privileges and access sensitive functionalities in Ech0. This bypasses least-privilege access controls. The confirmed impact includes unauthorized access to the /api/inbox and complete backup exports. Attackers can exfiltrate ZIP archives containing application databases and logs. This can lead to the exposure of user credentials, configuration data, and other confidential information. This vulnerability impacts organizations relying on access tokens for privilege separation and increases the risk of data breaches.

Recommendation

• Apply scope enforcement to all privileged routes in Ech0. Specifically, use the middleware.RequireScopes(...) function on routes like /api/inbox, /api/panel/comments*, /api/addConnect, /api/delConnect/:id, /api/migration/*, and /api/backup/export as suggested in the advisory.
• Move the /api/backup/export endpoint behind the authenticated router group and apply proper scope validation.
• Modify the internal/handler/backup/backup.go to preserve the existing authenticated viewer context (ctx.Request.Context()) instead of rebuilding a new identity from raw JWT claims.
• Upgrade Ech0 to version 4.3.5 or later to receive the official patch that addresses this vulnerability.
• Deploy the Sigma rule Detect Ech0 Backup Export with Token Parameter to detect attempts to exploit the vulnerable /api/backup/export endpoint.
• Review and audit all privileged routes in Ech0 to ensure proper scope validation is enforced.