{"id":"CVE-2026-58271","published":"2026-09-21T20:17:26.993","lastModified":"2026-09-21T20:17:26.993","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.","cvssScore":6.8,"cvssSeverity":"MEDIUM","cvssVector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N","cwes":["CWE-307"],"vendors":[],"products":[],"references":[{"url":"https://github.com/Sync-in/server/security/advisories/GHSA-274f-6w77-8qm9","tags":[]}],"exploitRefs":[{"url":"https://github.com/Sync-in/server/security/advisories/GHSA-274f-6w77-8qm9","tags":[]}],"hasPoc":true,"ai":{"summary":"The flaw allows an attacker to bypass multi-factor authentication (MFA) and gain full access by successfully guessing a TOTP code or directly disabling MFA.","exploitability":"Exploitation requires guessing a TOTP code, which is moderately hard due to the nature of time-based one-time passwords. Precondition: Access to the `/api/app/sync/register` endpoint.","blast_radius":"If exploited, this could lead to unauthorized access and full control over user accounts, potentially compromising sensitive data.","remediation":"Upgrade to Sync-in Server version 2.4.0 or later to apply the necessary security patches.","tags":["auth-bypass","mfa","api-exploit","jwt"],"model":"qwen2.5:7b-instruct","analyzedAt":"2026-09-22T06:18:49.814Z"}}