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Microsoft is facing a significant security vulnerability in its Windows operating system known as PhantomRPC, which allows for privilege escalation. Cybersecurity experts have expressed concern over the company's delayed response in issuing a patch for this flaw. The vulnerability resides within the Windows Remote Procedure Call (RPC) architecture and enables processes with impersonation privileges to elevate their permissions to SYSTEM level. Researcher Haidar Kabibo identified five distinct paths for exploitation, which require user interaction, coercion, or compromise of background services. Despite disclosing the vulnerability to Microsoft in September 2025, the company categorized it as moderately severe and did not issue a patch or a Common Vulnerabilities and Exposures (CVE) listing. Microsoft stated that the technique requires an already-compromised machine and emphasized the importance of following security best practices. Experts have criticized Microsoft's lack of action, arguing that it is operationally negligent and places the burden of risk management on users. In the absence of a patch, security professionals recommend focusing on access control and environmental hygiene to mitigate the risks associated with the vulnerability.