CVE-2026-58271
@sync-in/server vulnerable to TOTP Brute-Force via `POST /api/app/sync/register`
- State
- Published
- Severity
- 6.8 Medium
- Published
- Sep 21, 2026
- Updated
- Sep 24, 2026
- Reserved
- Jun 29, 2026
Description
Sync-in Server is an open-source platform for file storage, sharing, collaboration, and syncing. Prior to version 2.4.0, `POST /api/app/sync/register` accepts credentials and a TOTP code to register a desktop sync client. On a failed TOTP, `SyncClientsManager.register()` calls `updateAccesses(user, ip, false)`, which hits a freeze branch that writes `passwordAttempts` back unchanged. The counter never reaches `USER_MAX_PASSWORD_ATTEMPTS` (10) and the lockout gate never fires. A successful guess returns a `{clientId, clientToken}` pair. The token can be exchanged via `POST /api/app/sync/auth/cookie` for a full JWT. While the code is valid, the attacker can also call `POST /api/auth/2fa/disable` to permanently remove MFA. Version 2.4.0 patches the issue.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 3.1 | 6.8 Medium | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N | GitHub_M |
Weaknesses
- CWE-307 Improper Restriction of Excessive Authentication Attempts
Affected Products
| Product | Versions |
|---|---|
serverSync-in |
|
References
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