CVE-2026-49856
Received Received - Intake

SSRF Bypass via ICMP Probe in @jshookmcp/jshook

Publication date: 2026-08-13

Last updated on: 2026-08-13

Assigner: GitHub, Inc.

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.

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Meta Information

Published
2026-08-13
Last Modified
2026-08-13
Generated
2026-08-13
AI Q&A
2026-08-13
EPSS Evaluated
N/A
NVD
CVE-2026-49856
EUVD
EUVD-2026-58065

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
jshookmcp jshook to 0.3.2 (exc)
jshookmcp jshook 0.3.2
jshookmcp jshook to 0.3.2 (inc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

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Executive Summary

CVE-2026-49856 is an SSRF vulnerability in the @jshookmcp/jshook npm package version 0.3.1 and below. The central SSRF policy blocks access to private, loopback, link-local, and reserved network targets for most network tools. However, the ICMP probe and traceroute tools bypass this policy by resolving targets and invoking native functions directly without authorization checks. This allows an MCP client to probe internal addresses, revealing internal network reachability and route mapping from the server's position.

Detection Guidance

To detect this vulnerability, check if your system runs @jshookmcp/jshook version 0.3.1 or below. Look for unauthorized ICMP probe or traceroute requests targeting internal addresses like 10.0.0.1, 192.168.x.x, or 172.16.x.x. Monitor network logs for SSRF bypass attempts.

Impact Analysis

An attacker with access to the network domain could exploit this to probe internal network addresses like 10.0.0.1 or 192.168.x.x, mapping out internal infrastructure, measuring latency, and identifying reachable services. While it does not allow code execution or data exfiltration, it provides reconnaissance capabilities that could aid further attacks if combined with other vulnerabilities.

Mitigation Strategies

Upgrade to version 0.3.2 or later of @jshookmcp/jshook. Ensure the SSRF authorization policy is enforced for all network tools, including ICMP probe and traceroute. Remove or restrict access to vulnerable functions like resolveHostname().

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