CVE-2026-58269: Sync-in Server 2FA Bypass via POST /api/auth/token
Summary
CVE-2026-58269: Sync-in Server has a complete 2FA Bypass via POST /api/auth/token. Affects @sync-in/server versions < 2.4.0. Fixed in 2.4.0. How to fix ↓
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Background
Sync-in Server is an open-source application designed for user authentication and management, providing features such as token-based authentication and two-factor authentication (2FA) for enhanced security. The application supports TOTP (Time-based One-Time Password) for 2FA, which is intended to add an additional layer of security by requiring users to provide a second form of verification. However, a vulnerability has been identified in version 2.3.0 that allows attackers to bypass this 2FA mechanism under certain conditions.
Vulnerability Detail
The vulnerability arises from the token endpoint (POST /api/auth/token) that allows authentication using only a username and password, without checking if the account has TOTP 2FA enabled. An attacker with valid credentials for a 2FA-enabled account can obtain unrestricted Bearer access and refresh JWTs in a single request, effectively bypassing the 2FA requirement. This flaw is due to the implementation in the auth.controller.ts file, where the getTokens() function is called directly after validating the username and password, without enforcing the necessary 2FA checks. The potential ramifications include unauthorized access to user accounts and sensitive data, as the attacker can access protected API endpoints without needing the TOTP code.
How To Fix
Latest published version: 2.6.0 as of 23 Oct 2026
npm install @sync-in/server@2.6.0Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
2.4.0
This is the first release that contains the fix.
npm install @sync-in/server@2.4.0Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you can disable 2FA for accounts that are at risk until the package is updated. However, this is not recommended as it exposes accounts to potential unauthorized access. It is best to apply the patch as soon as possible.
Conclusion
The CVE-2026-58269 vulnerability in Sync-in Server allows attackers to bypass 2FA authentication, posing a significant security risk. It is crucial to update to version 2.4.0 or later to mitigate this issue and protect user accounts from unauthorized access.
See every vulnerability recorded for @sync-in/server →
FAQ
The CVSS score of this vulnerability is 8.1, indicating a high severity level.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in real-time. You can check your application using the Vulert playground without any signup at Vulert Scanner.
An attacker can gain unauthorized access to user accounts and sensitive data by bypassing the 2FA requirement, leading to potential data breaches.
Yes, a patch is available in version 2.4.0 of the Sync-in Server package. It is recommended to update to this version to mitigate the vulnerability.
If an immediate update is not possible, consider disabling 2FA for affected accounts as a temporary measure, but this is not recommended due to security risks.
References
Related vulnerabilities
Recent vulnerabilities recorded for @sync-in/server.
