Sync-in Server Updates Fix 2FA, ReDoS, and Login Enumeration Flaws
Tech GuruQuick Answer
Sync-in Server 2.4.1 includes fixes for four authentication and sync flaws. Three affect releases through 2.3.0; login-timing enumeration remains in 2.4.0. The risks differ: the two MFA attacks require known credentials, the regex denial of service requires sync access, and timing enumeration is unauthenticated.
Confirm Scope And Apply The Supported Fix
What to do now: Update the running server to 2.4.1, including deployed container instances. Check API-token MFA enforcement, desktop registration lockout, sync filters and login behavior with approved test accounts.
Last verified: 2026-09-22 UTC. Recheck the authoritative advisory and supported distribution channel before changing production.
Scope And Authority
| Product scope | @sync-in/server through 2.3.0, plus login-enumeration exposure through 2.4.0 |
|---|---|
| Advisory | GHSA-274f-6w77-8qm9 / GHSA-92cr-jxw4-5wjg / GHSA-jx63-h26r-8cph / GHSA-29hq-23m2-2j47 |
| CVEs | CVE-2026-58269, CVE-2026-58270, CVE-2026-58271, CVE-2026-58272 |
| Project advisory publication | 2026-06-22 through 2026-06-24 (four project advisories) |
| Recorded source timestamp (historical snapshot) | 2026-09-22 14:49:27 UTC |
| Affected versions | @sync-in/server through 2.3.0 for the 2FA bypass, TOTP brute force, and ReDoS issues; versions through 2.4.0 for login timing enumeration. |
| Fixed version | @sync-in/server 2.4.1, which includes the 2.4.0 security corrections |
| CVSS base score | 5.3 / 6.5 / 6.8 / 8.1 (CVSS v3.1) |
| CVSS severity | Medium to High |
| Exploitation status | Not stated by the authority; no exploitation claim is inferred. |
What Changed
CVE-2026-58269 lets someone with a valid password obtain unrestricted bearer tokens without completing TOTP. CVE-2026-58271 affects desktop-client registration: repeated incorrect TOTP codes do not advance the lockout counter. That attack additionally requires desktop sync permission.
CVE-2026-58270 allows an authenticated sync user to submit a costly pathFilters regex. With a matching worst-case file path, it can block the worker's event loop; the notice does not establish permanent failure after requests stop. CVE-2026-58272 exposes account existence because the missing-user login path skips password-hash work. This last issue requires 2.4.1 rather than 2.4.0.
What To Validate Now
- Inventory. Record server/package or container versions, TOTP settings, API-token consumers, desktop sync permissions and exposed login routes.
- Establish applicability. Compare each deployment with the authority's affected-version statement: @sync-in/server through 2.3.0 for the 2FA bypass, TOTP brute force, and ReDoS issues; versions through 2.4.0 for login timing enumeration. Do not infer applicability from product family or severity alone.
- Remediate. Apply @sync-in/server 2.4.1, which includes the 2.4.0 security corrections through the supported vendor or project channel, following the current advisory and change-control requirements.
- Validate. Confirm MFA is required before issuing unrestricted API tokens, failed registration attempts reach the configured lockout policy, ordinary sync filters still work, and invalid logins remain rejected. Assess timing with controlled repeated measurements; a single response proves neither a leak nor its absence.
- Retain evidence. Preserve asset and owner identifiers, the applicability decision, before-and-after versions, change approval, installation output, validation results, and any exception or rollback record.
Operational Cautions
Use the exact supported release stream and repository. Test dependencies, clusters, integrations, and rollback before broad deployment; a CVSS rating or reachable feature is not evidence of exploitation.
Evidence To Retain
- Exact product, release stream, package or application version, enabled feature, environment, and accountable owner.
- UTC timestamps, authority revision, approved change record, installer or package-manager output, and resulting version.
- Relevant logs and monitoring evidence, test results, exceptions, compensating controls, and rollback decisions.
Related TechGeeks Resources
Authoritative References
Correction policy: If the authority changes affected versions, fixed versions, severity, exploitation information, mitigations, or required action, TechGeeks will update this notice and its verification date.
