CVE-2026-79749
Received Received - Intake

SSRF Bypass via IPv6 Transition Addresses in MCPHub

Publication date: 2026-08-31

Last updated on: 2026-08-31

Assigner: GitHub, Inc.

Description
MCPHub is a unified hub for centrally managing and dynamically orchestrating multiple MCP servers/APIs into separate endpoints with flexible routing strategies. Prior to version 1.0.32, MCPHub's SSRF guard in src/utils/ssrf.ts uses a custom isBlockedIpv6 function that only checks for loopback, link-local, unique-local, IPv4-mapped, and IPv4-compatible IPv6 addresses. IPv6 transition address families -- NAT64 (64:ff9b::/96), 6to4 (2002::/16), and Teredo (2001::/32) -- are not checked. An attacker who can specify a URL for an MCP server connection can encode a private IPv4 address inside one of these IPv6 forms to bypass the SSRF guard and reach internal infrastructure. This issue has been patched in version 1.0.32.

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Meta Information

Published
2026-08-31
Last Modified
2026-08-31
Generated
2026-08-31
AI Q&A
2026-08-31
EPSS Evaluated
N/A
NVD
CVE-2026-79749
EUVD
EUVD-2026-68685

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
mcphub mcphub to 1.0.32 (exc)

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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

This is a Server-Side Request Forgery (SSRF) vulnerability in MCPHub versions before 1.0.32. The SSRF guard fails to block IPv6 transition addresses like NAT64, 6to4, and Teredo. Attackers can encode private IPv4 addresses in these IPv6 formats to bypass SSRF protection and access internal infrastructure.

Detection Guidance

Check MCPHub version with npm list mcphub. If <=1.0.31, the system is vulnerable. Inspect network logs for outbound connections to IPv6 transition addresses like NAT64 (64:ff9b::/96), 6to4 (2002::/16), or Teredo (2001::/32). Use tools like tcpdump or Wireshark to monitor for encoded private IPv4 addresses in IPv6 formats.

Impact Analysis

An attacker could exploit this to access internal services, such as cloud metadata endpoints (e.g., 169.254.169.254), by crafting malicious URLs. This could lead to unauthorized data exposure or service manipulation if the network supports IPv6 transition mechanisms.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating confidentiality requirements in GDPR and HIPAA. Organizations using vulnerable versions may face compliance breaches if internal systems are compromised.

Mitigation Strategies

Upgrade MCPHub to version 1.0.32 or later immediately. If upgrading is not possible, disable IPv6 transition mechanisms (NAT64, 6to4, Teredo) on the host network. Restrict outbound connections to trusted endpoints and review MCP server connection URLs for suspicious IPv6 encodings.

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