GHSA-q4x5-8cj6-52wg
Sync-in Server: SSRF protection bypass via IPv4-mapped IPv6 addresses in regExpPrivateIP
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | @sync-in/server | < 2.3.0 | 2.3.0 |
Details
As written in the advisory (Markdown source, shown as plain text).
Summary:
The private IP blocklist regex used in the URL download feature does not match IPv4-mapped IPv6 addresses (e.g. ::ffff:127.0.0.1), allowing SSRF protection to be bypassed on dual-stack systems.
Affected components
backend/src/applications/files/services/files-manager.service.ts – downloadFromUrl() checks regExpPrivateIP against request.socket.remoteAddress.
backend/src/applications/files/utils/url-file.ts – regExpPrivateIP does not include ::ffff:<ipv4> variants.
Details:
The regExpPrivateIP regex in backend/src/applications/files/utils/url-file.ts correctly blocks standard IPv4 private ranges but does not include ::ffff: prefixed variants. On dual-stack systems, Node.js can report a socket's remoteAddress in IPv4-mapped IPv6 form, meaning the check in FilesManager.downloadFromUrl() can be bypassed entirely.
PoC:
[poc.pdf](https://github.com/user-attachments/files/26990874/poc.pdf)
Proof:
<img width="1080" height="842" alt="1000226655" src="https://github.com/user-attachments/assets/797cea83-0a08-4a16-a91b-31c51068d473" />
Impact:
An attacker can supply a crafted URL pointing to an internal address that gets reported as ::ffff:127.0.0.1 or ::ffff:10.x.x.x, causing the server to fetch internal resources that should be blocked. Any user with access to the file download feature is a potential attacker.
References
External links from the advisory. They lead to third-party sites.