Sync-in Server has a complete 2FA Bypass via `POST /api/auth/token`

published 2026-09-21 48 d ago modified 2026-09-24 45 d ago also GHSA-92cr-jxw4-5wjg , EUVD-2026-84115

cvss: 8.1; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 19%
public exploits: 0; none known

Sync-in Server is an open-source platform for file storage, sharing, collaboration, and syncing. Prior to version 2.4.0, `POST /api/auth/token` authenticates with username and password only, then calls `getTokens()`, which returns full access and refresh JWTs without checking whether the account has TOTP 2FA enabled. An attacker with stolen or phished credentials can bypass 2FA in a single request. The parallel login endpoint (`POST /api/auth/login`) correctly enforces 2FA by calling `setCookies(user, res, true)`, which gates on `user.twoFaEnabled`. Version 2.4.0 patches the issue.

Patch / fix

fixed in 1 links 3

npm @sync-in/server 2.4.0

github.com/Sync-in/server@3ec74e2 commit
github.com/Sync-in/server#228 pull request
github.com/Sync-in/server/releases/tag/v2.4.0 release

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: total
Assessed: 45 d ago (2026-09-24)

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 19% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/Sync-in/server/security/advisories/GHSA-92cr-jxw4-5wjg referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	8.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
GitHub	3.1	8.1	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	@sync-in/server	<2.4.0	2.4.0

Affected products

Sync-in server

Classification

Weakness

CWE-288 Authentication Bypass Using an Alternate Path or Channel

References

github.com /Sync-in/server/pull/228
web
github.com /Sync-in/server/commit/3ec74e2ea1f538fe1a3ac9487bdf24a19e548361
web
github.com /Sync-in/server/security/advisories/GHSA-92cr-jxw4-5wjg
exploit, web
nvd.nist.gov /vuln/detail/CVE-2026-58269
advisory
github.com /Sync-in/server
package
github.com /Sync-in/server/releases/tag/v2.4.0
web

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary