{“lastseen”:”2026-04-29T14:11:22″,”description”:”A researcher has discovered a weakness called PhantomRPC that Microsoft does not consider a vulnerability it plans to patch.\\n\\nPhantomRPC involves Windows Remote Procedure Call (RPC), the core of communication between Windows processes. The vulnerability lets a process with impersonation rights escalate to SYSTEM by impersonating high\u2011privileged clients that connect to a fake RPC server.\\n\\nThe researcher presented a detailed technical report outlining five exploitation paths, including coercion, user interaction, or background services. They warned that potential vectors are \u201ceffectively unlimited\u201d because the root issue is architectural.\\n\\nMicrosoft, however, classified the issue as \u201cmoderate,\u201d refused a bounty, declined to assign a CVE (a spot in the list of Common Vulnerabilities and Exposures**)** , and closed the case without tracking. Its position is that the technique requires an already\u2011compromised machine and does not provide unauthenticated or remote access.\\n\\nExperts disagreed with Microsoft\u2019s assessment. Their concern is that Microsoft is downplaying a systemic local privilege escalation technique that exists in all supported Windows versions.\\n\\n## The issue\\n\\nAt the core of this issue is that the Windows RPC runtime does not sufficiently verify that the server a high\u2011privileged client connects to is the intended legitimate endpoint.\\n\\nIf a legitimate RPC server is not reachable (for example because the service stopped, was misconfigured, not installed, or due to a race condition), an attacker with SeImpersonatePrivilege can spin up a fake RPC server that \u201cfills the gap\u201d using the same interface and endpoint.\\n\\nWhen a SYSTEM or high\u2011privileged client connects to this fake server, using an impersonation level that allows the server to impersonate the client, the attacker can call `RpcImpersonateClient` and immediately escalate their privileges to SYSTEM.\\n\\nFrom Microsoft\u2019s perspective, the ability to run a rogue RPC server in this way falls under the category of \u201calready compromised.\u201d\\n\\n## SeImpersonatePrivilege\\n\\nTo understand the issue better, we need to dig into what SeImpersonatePrivilege does.\\n\\nBasically, SeImpersonatePrivilege is the Windows permission that lets a program \u201cpretend to be you\u201d after you\u2019ve already logged in, so it can do things on your behalf using your level of access.\\n\\nIt\u2019s needed because many system services and server\u2011type apps (file sharing, RPC servers, COM servers, web apps) have to perform actions on behalf of a user, like reading their files or applying group policy.\\n\\nIf an attacker gains this privilege, they can create a fake service or server and wait for a more powerful account to talk to it. When that high\u2011privilege service connects, the attacker can grab its security token and impersonate it, effectively upgrading from an account with lower privileges to full SYSTEM control on that machine.\\n\\n## Protection\\n\\nA Microsoft spokesperson provided the following statement:\\n\\n\\u003e \u201cThis technique requires an already-compromised machine and does not grant unauthenticated or remote access. Any update is a balance between existing compatibility and customer risk, and we remain committed to continually hardening our products. We recommend customers follow security best practices, including limiting administrative privileges and applying the principle of least privilege.\\”\\n\\nIn our opinion, mitigating PhantomRPC properly would require deep changes to the RPC architecture, which is hard to do on existing Windows versions without breaking compatibility. It’s maybe something we\u2019ll see in future versions, given the scale of change needed.\\n\\nWhat you can do:\\n\\n * As PhantomRPC is a piece in a larger chain, it is still very important to keep Windows updated.\\n * Use your admin account sparingly and only for the tasks that need that kind of privilege.\\n * Use an up-to-date, real-time anti-malware solution that can detect and block suspicious privilege\u2011escalation activity.\\n * Avoid disabling or \u201chardening\u201d services blindly since a malicious service might step in their place.\\n\\n\\n\\nTo answer the question in the title: it looks like a \\”feature\\” that can be abused in many ways; one that has outlived its original threat model. Defenders have to treat them as ongoing risks, rather than one\u2011off CVEs.\\n\\n* * *\\n\\n\\n\\n### ****\u201cOne of the best cybersecurity suites on the planet.\u201d** **\\n\\nAccording to CNET. Read their review \u2192\\n\\n* * *”,”published”:”2026-04-29T13:27:32″,”modified”:”2026-04-29T13:27:32″,”type”:”malwarebytes”,”title”:”Microsoft won\\u0026#8217;t patch PhantomRPC: Feature or bug?”,”source”:””,”references”:””,”id”:”MALWAREBYTES:EDF7965B2623B171FB9827274D3F71A7″,”bulletinFamily”:”blog”,”cwe”:null,”cvelist”:[],”sourceData”:””,”sourceHref”:””,”cvss”:{“score”:0,”severity”:”NONE”,”vector”:”NONE”,”version”:”NONE”},”cvss2″:{},”cvss3″:{“version”:””,”vectorString”:””,”baseScore”:0,”baseSeverity”:””,”attackVector”:””,”attackComplexity”:””,”privilegesRequired”:””,”userInteraction”:””,”scope”:””,”confidentialityImpact”:””,”integrityImpact”:””,”availabilityImpact”:””,”cvssV3″:{“version”:””,”vectorString”:””,”baseScore”:0,”baseSeverity”:””,”attackVector”:””,”attackComplexity”:””,”privilegesRequired”:””,”userInteraction”:””,”scope”:””,”confidentialityImpact”:””,”integrityImpact”:””,”availabilityImpact”:””}},”href”:”https:\/\/www.malwarebytes.com\/blog\/news\/2026\/04\/microsoft-wont-patch-phantomrpc-feature-or-bug”,”category_name”:”News”,”post_link”:””,”product”:””,”version”:””,”vendor”:””,”ai_description”:””,”ai_severity”:””,”ai_vendor”:””,”ai_product”:””,”ai_version”:””,”ai_score”:0}<\/p>\n","protected":false},"excerpt":{"rendered":"
{“lastseen”:”2026-04-29T14:11:22″,”description”:”A researcher has discovered a weakness called PhantomRPC that Microsoft does not consider a vulnerability it plans to patch.\\n\\nPhantomRPC involves Windows Remote Procedure Call (RPC),…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[6,8,12,115,13,33,7,11,5],"class_list":["post-50171","post","type-post","status-publish","format-standard","hentry","category-category_news","tag-cve","tag-cvss","tag-exploit","tag-malwarebytes","tag-news","tag-none","tag-security","tag-tapic","tag-vulnerability"],"yoast_head":"\n