CVE-2026-58272 Sync-in Server has Username/Login Enumeration via Timing Side-Channel on POST /api/auth/login (incomplete fix of the prior timing-attack advisory)
An unauthenticated attacker can enumerate valid usernames via timing side-channels in the login endpoint, facilitating credential stuffing and phishing attacks.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-58272?
CVE-2026-58272 is a medium-severity vulnerability in Sync-in server, published on 21 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-208
Which versions are affected by CVE-2026-58272?
2 open source packages ship an affected version, including @sync-in/server.
| Package | Affected | Fixed in |
|---|---|---|
@sync-in/server npm | All versions | 2.4.1 |
@sync-in/server npm | All versions | 2.4.1 |
How do I fix CVE-2026-58272?
Upgrade @sync-in/server to 2.4.1 or later.
Is CVE-2026-58272 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58272 exists.
Sources
Also known as GHSA-29hq-23m2-2j47.