What happened
NVD published this CVSS 5.1 Medium vulnerability on Sept 18, 2026 describing a DNS-rebinding-exploitable authentication gap in a local process orchestrator's MCP interface.
Why it matters
This is part of a recurring class of MCP SSE/HTTP transport implementations that omit Host/Origin validation, letting any webpage a developer visits pivot into local developer tooling and orchestrated processes — a low-cost but recurring class of exposure across the MCP ecosystem.
Attack vector
The MCP SSE listener accepts browser-origin requests to /sse and its message endpoint without validating the Host header, validating the Origin header, or requiring caller authentication, enabling a malicious website to use DNS rebinding to control a developer's local MCP SSE session.
Affected systems
Process Compose prior to 1.120.0
Mitigation
Upgrade to Process Compose 1.120.0 or later per the vendor's GitHub commit fix.