CVE-2026-58272 in server
Summary
by MITRE • 09/22/2026
Sync-in Server is an open-source platform for file storage, sharing, collaboration, and syncing. Versions prior to 2.4.1 contain an observable timing discrepancy in the login endpoint because authentication attempts for nonexistent accounts return without performing the bcrypt comparison used for existing accounts. An unauthenticated attacker can measure response times to enumerate valid usernames or email addresses, facilitating credential-stuffing, password-spraying, and phishing attacks. Version 2.4.1 contains a patch.
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Analysis
by VulDB Data Team • 09/22/2026
Sync-in Server versions prior to release 2.4.1 exhibit an observable timing discrepancy within the authentication endpoint that facilitates user enumeration through side-channel analysis. The core technical flaw lies in the implementation of the login logic, where the system handles requests for non-existent accounts differently than those for valid users. Specifically, when a request is made with credentials belonging to an account that does not exist in the database, the server returns immediately without executing the computationally intensive bcrypt hashing comparison. In contrast, authentication attempts against existing accounts trigger the full password verification process, which involves generating a salt and performing multiple rounds of hashing before returning a response. This difference creates a measurable latency gap between valid and invalid username submissions, allowing an attacker to distinguish between them based on response time alone.
This vulnerability aligns with CWE-208, which describes observable timing discrepancy as a class of weakness where sensitive information can be inferred by measuring the time taken for operations to complete. By systematically varying usernames or email addresses in login requests and recording the server's response times, an unauthenticated attacker can build a list of valid accounts within the Sync-in Server instance. This capability effectively neutralizes one layer of defense against brute-force attacks, as it allows the attacker to filter out invalid targets before expending resources on password guessing. The vulnerability is particularly dangerous because it requires no prior authentication and relies solely on network latency measurements, which can be performed remotely over standard HTTP connections.
The operational impact of this timing-based enumeration is significant for organizations relying on Sync-in Server for secure file storage and collaboration. Once valid usernames are identified through the timing side-channel, attackers can proceed with more targeted attacks such as credential stuffing or password spraying. Credential stuffing involves using leaked credentials from other breaches to attempt login against the discovered accounts, while password spraying entails trying a few common passwords across many different user accounts to avoid account lockout mechanisms that typically trigger after multiple failed attempts for a single user. Furthermore, knowing which email addresses are registered allows attackers to conduct highly personalized phishing campaigns, increasing the likelihood of social engineering success by referencing specific organizational details or services associated with those verified identities.
To mitigate this vulnerability, organizations running Sync-in Server must upgrade immediately to version 2.4.1 or later, where the developers have implemented a patch that ensures consistent response times regardless of whether the account exists. This mitigation typically involves performing the bcrypt comparison for all login attempts, including those for non-existent users, thereby eliminating the timing difference that attackers exploit. In addition to upgrading, administrators should implement rate limiting on the authentication endpoint to slow down automated enumeration tools and monitor logs for unusual patterns in login requests from single source IPs or user agents. Integrating multi-factor authentication further reduces risk by ensuring that even if valid credentials are obtained through subsequent attacks, unauthorized access remains blocked without the second factor of verification.
From a threat intelligence perspective, this vulnerability maps to MITRE ATT&CK technique T1087, Account Discovery, specifically under the sub-technique for local account enumeration via timing analysis. It also relates to T1110, Brute Force, as it serves as an initial reconnaissance step that enables more efficient credential attacks. Security teams should treat this not merely as a configuration issue but as a fundamental architectural flaw in how authentication responses are handled. Regular security assessments and penetration testing should include checks for timing-based side channels on all authentication endpoints to ensure that no such discrepancies exist within the application logic, thereby maintaining robust defense-in-depth strategies against automated reconnaissance tools.