CVE-2026-49856 @jshookmcp/jshook: ICMP probe and traceroute skip local-network SSRF authorization
Attackers can bypass SSRF protections in the jshook MCP server to probe internal network addresses via ICMP and traceroute tools.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-49856?
CVE-2026-49856 is a medium-severity server-side request forgery vulnerability in vmoranv jshookmcp, published on 13 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
@jshookmcp/jshook is an MCP server that gives AI agents tools for JavaScript analysis and security research. In version 0.3.1, he network domain has a central SSRF authorization policy that blocks private, loopback, link-local, and reserved targets unless an explicit authorization object allows private network access. The policy is enforced by raw HTTP/TCP/TLS RTT tools, but the ICMP probe and traceroute tools resolve the target and invoke the native ICMP/traceroute sink directly. An MCP client with access to an active network domain can therefore ask the jshookmcp server to probe internal addresses even when local SSRF access is disabled for the other raw network tools. This exposes an internal reachability and route mapping primitive from the server network position. Version 0.3.2 fixes the issue.
Weakness: CWE-918
Which versions are affected by CVE-2026-49856?
2 open source packages ship an affected version, including @jshookmcp/jshook.
| Package | Affected | Fixed in |
|---|---|---|
@jshookmcp/jshook npm | From 0.3.1 | 0.3.2 |
@jshookmcp/jshook npm | From 0.3.1 | 0.3.2 |
How do I fix CVE-2026-49856?
Upgrade @jshookmcp/jshook to 0.3.2 or later.
Upgrade, and send outbound requests through an allow-list that blocks internal addresses. More about Server-side request forgery.
Is CVE-2026-49856 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49856 exists.
Sources
Also known as GHSA-c5r6-m4mr-8q5j.