GeiserX genieacs-mcp up to 0.3.1 Streamable HTTP transport cmd/server/main.go Start dns rebinding

Summaryinfo

A vulnerability identified as critical has been detected in GeiserX genieacs-mcp up to 0.3.1. Affected by this issue is the function Home of the file cmd/server/main.go of the component Streamable HTTP transport. Performing a manipulation results in dns rebinding. This vulnerability is reported as CVE-2026-55637. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability was found in GeiserX genieacs-mcp up to 0.3.1. It has been classified as critical. This affects the function Start of the file cmd/server/main.go of the component Streamable HTTP transport. The manipulation with an unknown input leads to a dns rebinding vulnerability. CWE is classifying the issue as CWE-350. The product performs reverse DNS resolution on an IP address to obtain the hostname and make a security decision, but it does not properly ensure that the IP address is truly associated with the hostname. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

genieacs-mcp is an MCP server for GenieACS written in Go. Prior to 0.3.2, the Streamable HTTP transport in cmd/server/main.go creates an unauthenticated /mcp listener on the default MCP_LISTEN_ADDR value 127.0.0.1:8080 when MCP_AUTH_TOKEN is unset and the httpSrv.Start(addr) branch does not validate the Host or Origin headers. A malicious website can use DNS rebinding to send browser requests with attacker-controlled Host and Origin values to the loopback listener, initialize an MCP session, list tools, and invoke operations against the GenieACS NBI configured by ACS_URL. Successful exploitation can expose or modify CPE management state, including device reboots, firmware tasks, TR-069 parameter changes, presets, provisions, tags, connection requests, and task operations. The npm wrapper is not affected because it forces TRANSPORT=stdio and does not expose an HTTP listener. This issue is fixed in version 0.3.2.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-55637 since 06/17/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1583.002 according to MITRE ATT&CK.

Upgrading to version 0.3.2 eliminates this vulnerability.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• GeiserX

Name

• genieacs-mcp

Version

• 0.3.0
• 0.3.1

Website

• Product: https://github.com/GeiserX/genieacs-mcp/

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