@sync-in/server vulnerable to TOTP Brute-Force via POST /api/app/sync/register

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.8 · CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-58271: 0.22% estimated exploitation activity in the next 30 days; percentile 12.48 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Affected component: Sync-in Server v2.3.0, POST /api/app/sync/register. Required attacker capability: Valid login and password for a TOTP-enabled account with desktop sync permission. Summary POST /api/app/sync/register accepts credentials and a TOTP code to register a desktop sync client. In the vulnerable version, on a failed TOTP attempt, SyncClientsManager.register() called updateAccesses(user, ip, false), which hit a freeze branch that wrote passwordAttempts back unchanged. The counter never reached USERMAXPASSWORDATTEMPTS (10), so the account lockout gate never fired for repeated TOTP failures through this endpoint. A successful TOTP guess registers a sync client and returns a {clientId, clientToken} pair, provided the account has the required desktop app permission and the registration payload is valid. The token can then be exchanged via POST /api/app/sync/auth/cookie for an authenticated session. While the guessed TOTP code is still valid, and because the attacker already…

Published by the source

22 Sep 2026, 14:44 UTC

Last modified by the source

22 Sep 2026, 15:00 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-274f-6w77-8qm9

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-274f-6w77-8qm9

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-274f-6w77-8qm9

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# Patch Next advisory brief: CVE-2026-58271

Advisory: @sync-in/server vulnerable to TOTP Brute-Force via `POST /api/app/sync/register`
IDs: CVE-2026-58271, GHSA-274f-6w77-8qm9
Record: https://patchnext.com/advisories/cve-2026-58271 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @sync-in/server 2.4.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @sync-in/server: affected <= 2.3.0; fixed in 2.4.0

## Suggested inspection (read-only)
- `npm ls @sync-in/server --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @sync-in/server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-274f-6w77-8qm9 (GitHub-reviewed advisory GHSA-274f-6w77-8qm9 lists affected ranges: npm @sync-in/server >=0 <=2.3.0)
- Verified: https://osv.dev/vulnerability/GHSA-274f-6w77-8qm9 (OSV record GHSA-274f-6w77-8qm9 lists affected ranges: npm @sync-in/server >=0 <2.4.0 (fixed))

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