CVE-2026-58271

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.

• CWE-307

• https://github.com/Sync-in/server/security/advisories/GHSA-274f-6w77-8qm9

Published

Sep 21, 2026

Last Modified

Sep 21, 2026

Status

Received

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-58264FluidSynth is a software synthesizer based on the SoundFont …9.8
• CVE-2026-58266Anki is a program for creating and reviewing flashcards. Pri…6.5
• CVE-2026-58268SIPGO is a library for writing SIP services in the GO langua…7.5
• CVE-2026-58269Sync-in Server is an open-source platform for file storage, …8.1
• CVE-2026-5827A vulnerability has been found in code-projects Simple IT Di…7.3
• CVE-2026-58270Sync-in Server is an open-source platform for file storage, …6.5
• CVE-2026-58272Sync-in Server is an open-source platform for file storage, …5.3
• CVE-2026-58275Missing authorization in Azure DNS allows an unauthorized at…9.8
• CVE-2026-58276Use after free in Microsoft Edge (Chromium-based) allows an …7.5
• CVE-2026-58277Improper authorization in Microsoft Office SharePoint allows…8.8
• CVE-2026-58278Server-side request forgery (ssrf) in Microsoft Edge (Chromi…5.4
• CVE-2026-58279Missing authorization in Azure CycleCloud allows an authoriz…6.5