Metalama's Visual Studio integration uses a local named pipe for inter-process communication that deserializes messages without restricting CLR types, enabling local code execution. This unsafe deserialization affects all Metalama releases from 2023.0 through 2026.1.18 and is fixed in 2026.1.19. The pipe is accessible only by processes running as the same user, limiting exploitation to local same-user attackers. The vulnerability allows arbitrary code execution within the Visual Studio processes hosting Metalama components, impacting confidentiality, integrity, and availability of those processes. The practical severity is medium due to the same-user restriction and lack of privilege escalation. Remediation requires upgrading to Metalama 2026.1.19 or later, or updating affected Visual Studio extensions accordingly.