CVE-2017-10971 in X Server
Summary
by MITRE
In the X.Org X server before 2017-06-19, a user authenticated to an X Session could crash or execute code in the context of the X Server by exploiting a stack overflow in the endianness conversion of X Events.
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Analysis
by VulDB Data Team • 08/29/2025
The vulnerability identified as CVE-2017-10971 represents a critical stack overflow flaw within the X.Org X server implementation that existed prior to the June 19, 2017 release. This vulnerability specifically targets the endianness conversion process of X Events, which are fundamental communication elements between X clients and the X server in the X Window System. The flaw enables authenticated users within an X session to potentially execute arbitrary code or cause system crashes, fundamentally compromising the security and stability of graphical environments that rely on X11.
The technical root cause of this vulnerability lies in improper handling of endianness conversion during X Event processing. When X clients communicate with the X server, they must account for different byte order conventions between systems. The X server's implementation contained a flaw in its stack-based buffer management during these conversions, where insufficient bounds checking allowed maliciously crafted X events to overflow stack buffers. This particular vulnerability falls under CWE-121, which addresses stack-based buffer overflow conditions, and specifically relates to the improper handling of data conversion processes in network protocols. The flaw manifests when an authenticated user sends specially crafted X events that trigger the overflow during endianness conversion routines.
The operational impact of this vulnerability extends beyond simple system crashes to include potential code execution privileges within the X server context. Since the X server typically runs with elevated privileges to manage graphical display resources, successful exploitation could allow attackers to execute arbitrary code with the same privileges as the X server itself. This creates a significant risk for desktop environments, remote desktop sessions, and any system where X11 is utilized for graphical user interfaces. The vulnerability affects systems where the X server handles untrusted input from authenticated users, making it particularly dangerous in multi-user environments or systems with remote access capabilities.
Mitigation strategies for CVE-2017-10971 primarily focus on updating the X.Org X server to versions released after June 19, 2017, which contain the necessary patches addressing the stack overflow in endianness conversion routines. System administrators should also implement network segmentation to limit X server access to trusted networks, employ X server access controls to restrict client connections, and consider implementing monitoring solutions to detect unusual X event patterns that might indicate exploitation attempts. Additionally, organizations should follow the ATT&CK framework's principle of defending against privilege escalation techniques by ensuring that X server processes run with minimal necessary privileges and by implementing proper input validation mechanisms. The vulnerability demonstrates the importance of robust buffer management in network protocol implementations and serves as a reminder of the critical security implications of seemingly minor data conversion routines in system-level software components.