CVE-2026-77339

Overview

Process Compose prior to version 1.120.0 contains a security vulnerability in its MCP Server-Sent Events listener where browser-origin requests lack Origin header, Host header, and authentication validation. This allows malicious websites to leverage DNS rebinding to interact with the local loopback listener. When combined with exposed control tools, unauthorized attackers can execute administrative actions against local processes.

Description

Process Compose is a scheduler and orchestrator for non-containerized applications. Prior to 1.120.0, the MCP SSE listener in src/mcp/server.go accepts browser-origin requests to /sse and the returned message endpoint without validating the Host header, validating the Origin header, or authenticating the caller. When MCP SSE is enabled, a malicious website can use DNS rebinding to reach the loopback listener and issue MCP requests. If expose_control_tools is enabled, the attacker can enumerate process state, read or search logs, truncate logs, and start, stop, restart, or scale local processes; configured user-defined tools can expose additional commands and output. The Gin REST API token middleware does not protect this separately started MCP listener. This issue is fixed in version 1.120.0.

Impact

The vulnerability impacts confidentiality, integrity, and availability of managed local processes and their logs. Attackers using DNS rebinding can enumerate process states, read, search, or truncate logs, and manage process lifecycles including starting, stopping, restarting, and scaling. Users running Process Compose with the MCP SSE listener and control tools enabled on default loopback configurations are at risk.

Remediation

Upgrade Process Compose to version 1.120.0 or later where the MCP SSE listener properly validates headers and requests. Restrict the exposure of control tools (expose_control_tools) when using the MCP SSE feature unless strictly necessary.

Risk context

The vulnerability is rated with a CVSS v3 score of 5.3 and CVSS v4 of 5.1, categorizing it as medium severity. While exploitation requires a user to visit a malicious website enabling DNS rebinding, the potential impact on local process orchestration warrants prompt patching.

Affected products

• Fardog Process Compose