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[ CVE-2026-58272 · Published 21 Sep 2026 ]

Sync-in Server has Username/Login Enumeration via Timing Side-Channel on POST /api/auth/login (incomplete fix of the prior timing-attack advisory)

CVSS 5.3 EPSS <1%Fix available

[ Why it matters ]Priority signals

  • Public proof-of-concept exploit exists (CISA SSVC)

[ Description ]Official description

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.

[ Fixes ]Fixes and patches

  • @sync-in/server 2.4.1Fixed version · GitHub Advisories · npm package @sync-in/server: upgrade to 2.4.1 or later (affected <= 2.4.0)

[ Packages ]Affected open-source packages

[ References ]References