# CVE-2026-47684: Sync-in Server SSRF bypass via IPv4-mapped IPv6 addresses

Source: https://junglewise.ai/threats/cve-2026-47684-sync-in-server-ssrf-bypass-via-ipv4-mapped-ipv6-addresses  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-16. Updated: 2026-06-16  
License: CC BY 4.0 with a link back

CVE-2026-47684 · Severity: high · CVSS 7.7 · Published 2026-06-16

Sync-in Server is an open-source platform used for file storage, sharing, and collaboration. A security flaw in its URL download feature allows users to bypass safety filters and force the server to access internal network resources. This could lead to the exposure of sensitive internal data or unauthorized access to other services running on the organization's private network.

Technologies: [@sync-in/server (npm)](https://junglewise.ai/threats/technologies/sync-in-server). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-47684 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47684 being exploited in the wild.

**How severe is CVE-2026-47684?** High severity, with a CVSS score of 7.7, published 16 June 2026.

**Which products and versions are affected?** @sync-in/server (npm) <= 2.2.1, SEMVER:introduced=0,fixed=2.3.0.

**Is there a fix for CVE-2026-47684?** Yes. @sync-in/server (npm): upgrade to 2.3.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-47684 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-47684?** Check whether you run @sync-in/server (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @sync-in/server (npm): upgrade to 2.3.0 or later

  ```sh
  npm install @sync-in/server@2.3.0
  ```


## Technical details

A Server-Side Request Forgery (SSRF) vulnerability exists in Sync-in Server's 'downloadFromUrl' function within the FilesManager service. The root cause is an incomplete regular expression in the 'regExpPrivateIP' utility, which fails to account for IPv4-mapped IPv6 addresses (e.g., ::ffff:127.0.0.1). On dual-stack systems, an authenticated attacker can provide a crafted URL that bypasses the private IP blocklist, allowing the server to fetch resources from the local loopback or internal network. This vulnerability is patched in version 2.3.0, which strengthens SSRF protections against DNS rebinding, unsafe redirects, and proxy bypasses.

## Affected products

- Sync-in Sync-in Server <= 2.2.1

## Identifiers

- CVE-2026-47684
- GHSA-q4x5-8cj6-52wg

## Timeline

- 2026-05-22: patched: Version 2.3.0 released
- 2026-06-16: disclosed: CVE-2026-47684 published

## References

- [https://github.com/Sync-in/server/releases/tag/v2.3.0](https://github.com/Sync-in/server/releases/tag/v2.3.0)
- [https://github.com/Sync-in/server/security/advisories/GHSA-q4x5-8cj6-52wg](https://github.com/Sync-in/server/security/advisories/GHSA-q4x5-8cj6-52wg)

## Related threats

- [Sync-in Server has Username/Login Enumeration via Timing Side-Channel on POST /api/auth/login (incomplete fix of the prior timing-attack advisory)](https://junglewise.ai/threats/cve-2026-58272-sync-in-server-username-enumeration-via-timing-side-channel-in)
- [Sync-in Server ReDoS via unsanitized regex in pathFilters](https://junglewise.ai/threats/cve-2026-58270-sync-in-server-redos-via-unsanitized-regex-in-pathfilters)
- [@sync-in/server vulnerable to TOTP Brute-Force via `POST /api/app/sync/register`](https://junglewise.ai/threats/cve-2026-58271-sync-in-server-totp-brute-force-in-sync-registration)
- [Sync-in Server two-factor authentication bypass in token endpoint](https://junglewise.ai/threats/cve-2026-58269-sync-in-server-two-factor-authentication-bypass-in-token-endpoint)
- [Sync-in Server username enumeration via timing attack in login endpoint](https://junglewise.ai/threats/cve-2026-41161-sync-in-server-has-username-enumeration-via-timing-attack)