Executive brief
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.
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
Timeline
- 2026-05-22: patched: Version 2.3.0 released
- 2026-06-16: disclosed: CVE-2026-47684 published