In a significant cybersecurity development, a Google security researcher has uncovered a critical vulnerability that has remained unaddressed for two decades in Microsoft Windows. This flaw, tracked as CVE-2019-1162, affects all versions of the operating system, from Windows XP to the latest iteration, Windows 10. Following the recent patch Tuesday updates, Microsoft has now rectified this vulnerability, which was linked to the Windows management of Advanced Local Procedure Call (ALPC) and the way MSCTF clients and servers communicate.
The vulnerability allows an attacker, even one with limited privileges or operating from a sandboxed environment, to read and write data from higher-privileged applications. The MSCTF, or Microsoft Collaborative Translation Framework, is a component of the Text Services Framework within Windows. It oversees the management of input methods, keyboard layouts, text processing, and speech recognition.
When a user logs into a Windows machine, a CTF Mon service initiates, functioning as a centralized manager that orchestrates communication among various clients, which represent different application windows within the same user session. As noted by researcher Tavis Ormandy, this service plays a crucial role in notifying applications about changes in input methods and keyboard settings. The kernel mandates that applications connect to this service upon startup, allowing them to exchange messages and notifications with other applications.
Ormandy highlighted a significant security oversight: the absence of access controls or authentication measures during these interactions. Consequently, any application—regardless of user permissions—could connect to the CTF Mon’s ALPC port across all sessions. This means that attackers could potentially hijack an active user session to seize control over any application, even those running with elevated administrative privileges.
Further analysis revealed that the vulnerability does not merely facilitate access to other applications; it enables attackers to masquerade as a CTF service, tricking legitimate applications into interacting with them. This bypasses User Interface Privilege Isolation (UIPI), raising the risk that unprivileged processes could extract sensitive data, such as passwords, from any visible application window, gain SYSTEM-level access, or manipulate User Account Control (UAC) consent dialogs.
In addition to the primary vulnerability, Ormandy pointed out multiple memory corruption flaws within the CTF protocol itself. Even in its default configuration, the protocol’s framework permits application interaction, which could lead to widespread exploitation if left unaddressed. He has made public a custom open-source tool designed to explore the vulnerabilities within the CTF protocol, which he developed as part of his research.
Ormandy’s responsible disclosure to Microsoft took place in mid-May of this year. However, due to the company’s failure to implement a fix within 90 days, he publicly released the details, thereby alerting the security community to this critical issue.
Cybersecurity experts have drawn connections between this vulnerability and potential MITRE ATT&CK matrix tactics, categorizing it under initial access and privilege escalation. Attackers exploiting this flaw could utilize techniques that involve bypassing security mechanisms to gain unauthorized access to sensitive systems.
Business owners and IT professionals should take heed of this profound vulnerability, ensuring they remain vigilant and proactive in updating their systems to mitigate exposure to such threats.