CVE-2026-58271: CWE-307: Improper Restriction of Excessive Authentication Attempts in Sync-in server
Sync-in Server versions prior to 2.4.0 contain a vulnerability in the authentication mechanism where excessive authentication attempts are not properly restricted. Specifically, failed TOTP (Time-based One-Time Password) attempts do not increment the password attempt counter, preventing account lockout. This flaw allows an attacker to repeatedly guess TOTP codes without triggering lockout, potentially obtaining client tokens that can be exchanged for full JWTs. Additionally, the attacker can disable MFA via an API call. Version 2.4.0 includes a patch for this issue.
AI Analysis
Technical Summary
The Sync-in Server before version 2.4.0 has an improper restriction of excessive authentication attempts (CWE-307) in the endpoint POST /api/app/sync/register. On failed TOTP verification, the password attempt counter is not incremented, preventing the lockout mechanism from activating. Successful guesses yield clientId and clientToken pairs, which can be exchanged for JWTs via another API endpoint. Moreover, the attacker can disable MFA permanently using POST /api/auth/2fa/disable. This vulnerability is fixed in version 2.4.0.
Potential Impact
An attacker can perform unlimited TOTP guesses without triggering account lockout, increasing the risk of unauthorized access. Successful exploitation allows obtaining client tokens and full JWTs, leading to potential account compromise. The ability to disable MFA further reduces account security, increasing the likelihood of unauthorized access. The CVSS 3.1 score is 6.8 (medium severity) reflecting high confidentiality and integrity impact but requiring high attack complexity and low privileges.
Mitigation Recommendations
Upgrade Sync-in Server to version 2.4.0 or later, where this vulnerability is patched. No other mitigations are indicated by the vendor advisory. Patch status is confirmed by the version fix information.
CVE-2026-58271: CWE-307: Improper Restriction of Excessive Authentication Attempts in Sync-in server
Description
Sync-in Server versions prior to 2.4.0 contain a vulnerability in the authentication mechanism where excessive authentication attempts are not properly restricted. Specifically, failed TOTP (Time-based One-Time Password) attempts do not increment the password attempt counter, preventing account lockout. This flaw allows an attacker to repeatedly guess TOTP codes without triggering lockout, potentially obtaining client tokens that can be exchanged for full JWTs. Additionally, the attacker can disable MFA via an API call. Version 2.4.0 includes a patch for this issue.
CVSS v3.1
Score 6.8medium
Affected software
Sync-in
server
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Sync-in Server before version 2.4.0 has an improper restriction of excessive authentication attempts (CWE-307) in the endpoint POST /api/app/sync/register. On failed TOTP verification, the password attempt counter is not incremented, preventing the lockout mechanism from activating. Successful guesses yield clientId and clientToken pairs, which can be exchanged for JWTs via another API endpoint. Moreover, the attacker can disable MFA permanently using POST /api/auth/2fa/disable. This vulnerability is fixed in version 2.4.0.
Potential Impact
An attacker can perform unlimited TOTP guesses without triggering account lockout, increasing the risk of unauthorized access. Successful exploitation allows obtaining client tokens and full JWTs, leading to potential account compromise. The ability to disable MFA further reduces account security, increasing the likelihood of unauthorized access. The CVSS 3.1 score is 6.8 (medium severity) reflecting high confidentiality and integrity impact but requiring high attack complexity and low privileges.
Mitigation Recommendations
Upgrade Sync-in Server to version 2.4.0 or later, where this vulnerability is patched. No other mitigations are indicated by the vendor advisory. Patch status is confirmed by the version fix information.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-29T21:54:30.332Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6ab18d4c55bf5e2cf5653f7a
Added to database: 09/21/2026, 20:02:20 UTC
Last enriched: 09/21/2026, 20:16:45 UTC
Last updated: 09/21/2026, 20:48:35 UTC
Views: 6
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