CVE-2017-10972 in X Server
Summary
by MITRE
Uninitialized data in endianness conversion in the XEvent handling of the X.Org X Server before 2017-06-19 allowed authenticated malicious users to access potentially privileged data from the X server.
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Analysis
by VulDB Data Team • 08/29/2025
The vulnerability identified as CVE-2017-10972 represents a critical security flaw in the X.Org X Server that existed prior to the 2017-06-19 release. This issue stems from improper handling of uninitialized data during endianness conversion processes within the XEvent processing subsystem, creating a pathway for authenticated attackers to potentially access sensitive privileged information from the X server. The vulnerability specifically affects the X11 protocol implementation that governs graphical user interface communications between clients and the X server, making it particularly concerning for systems relying on graphical interfaces.
The technical root cause of this vulnerability lies in the XEvent handling mechanism where the X server fails to properly initialize data structures before performing endianness conversion operations. When processing XEvents, the server performs byte order conversions to ensure compatibility between clients and the server, but this process does not adequately initialize memory regions. This uninitialized data exposure creates a potential information disclosure channel where malicious authenticated users could read memory contents that should remain private or privileged. The vulnerability is classified under CWE-457 as "Use of Uninitialized Variable" and specifically relates to improper initialization of data structures during protocol processing.
From an operational impact perspective, this vulnerability enables authenticated malicious users to potentially access privileged data that should be restricted to authorized processes or users. The X server typically handles various graphical operations and maintains sensitive state information about connected clients, window management data, and potentially user session details. Attackers could exploit this weakness to extract information that might aid in further exploitation attempts or to gain insights into the system's internal state. The impact is particularly significant in multi-user environments or systems where the X server manages sensitive graphical sessions, as it could potentially lead to privilege escalation or information disclosure attacks that violate the principle of least privilege.
The exploitation of this vulnerability requires authentication to the X server, which limits its scope compared to unauthenticated attacks but still represents a serious security concern. The attack vector involves sending specially crafted XEvents that trigger the uninitialized data access during endianness conversion, potentially allowing attackers to read memory contents that contain sensitive information. Security practitioners should note that this vulnerability aligns with ATT&CK technique T1005 as "Data from Local System" and could contribute to broader reconnaissance activities. Organizations should implement immediate mitigations including updating to the patched X.Org X Server version released on 2017-06-19, which properly initializes data structures before endianness conversion operations. Additionally, monitoring for unusual XEvent patterns and implementing proper access controls for X server connections can help detect and prevent exploitation attempts. The vulnerability demonstrates the importance of proper memory initialization in protocol implementations and highlights the need for comprehensive security testing of core system components that handle user input and data processing.