CVE-2026-58271: medium-severity vulnerability in Sync-in server
@sync-in/server vulnerable to TOTP Brute-Force via `POST /api/app/sync/register`
Published · Updated
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.8epss 0.2%
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.
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Affected products
Sync-in · serverRelated CVEs — Sync-in server
In the same product, most dangerous first.
CVE-2026-58270MEDIUMSync-in Server has a ReDoS via Unsanitized Regex in Sync Diff `pathFilters`EPSS 0.4%CVE-2026-58272MEDIUMSync-in Server has Username/Login Enumeration via Timing Side-Channel on POST /api/auth/login (incomplete fix of the prior timing-attack advisory)EPSS 0.4%CVE-2026-41161MEDIUMUsername Enumeration via Timing AttackEPSS 0.3%CVE-2026-58269HIGHSync-in Server has a complete 2FA Bypass via `POST /api/auth/token`EPSS 0.3%CVE-2026-47684HIGHSync-in Server: SSRF protection bypass via IPv4-mapped IPv6 addresses in regExpPrivateIPEPSS 0.2%