Description

Researchers at 0patch recently uncovered an unpatched flaw in the Windows Remote Access Connection Manager (RasMan) service while examining a separate vulnerability that had already received a fix. Their analysis began with CVE-2025-59230, an elevation-of-privilege issue addressed in Microsoft’s October 2025 updates. While reviewing an exploit for this bug, the team noticed that it enabled arbitrary code execution as Local System from a non-administrative account—and that the exploit contained additional logic hinting at another, previously unknown weakness. CVE-2025-59230 is rooted in a race condition involving RasMan’s RPC endpoint. When RasMan starts, it registers an endpoint trusted by several privileged services. If an attacker manages to register this endpoint before RasMan does, those services may unknowingly communicate with a malicious process. However, this race window is almost nonexistent because RasMan typically starts automatically during system boot. As 0patch noted, even a scheduled task created by an attacker would not launch quickly enough to exploit the race unless RasMan could first be stopped. This requirement led researchers to the second flaw: a crash bug in RasMan that any unprivileged user can trigger, effectively forcing the service to restart and making the race condition exploitable. The issue stemmed from improper handling of a circular linked list. During iteration, the code failed to exit when encountering a NULL pointer and instead attempted to read through it, resulting in an immediate memory access violation and service crash. Microsoft has been notified and is expected to deliver an official fix in a future update. In the meantime, 0patch has deployed a micropatch that introduces a correct NULL check to prevent the crash and block the privilege-escalation chain. These micropatches are available for multiple supported Windows versions, including Windows 10, Windows 11 (21H2–25H2), as well as older platforms such as Windows 7 and Server 2008 R2.