CVE-2014-8091 in X11
Summary
by MITRE
X.Org X Window System (aka X11 and X) X11R5 and X.Org Server (aka xserver and xorg-server) before 1.16.3, when using SUN-DES-1 (Secure RPC) authentication credentials, does not check the return value of a malloc call, which allows remote attackers to cause a denial of service (NULL pointer dereference and server crash) via a crafted connection request.
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Analysis
by VulDB Data Team • 08/29/2025
The vulnerability identified as CVE-2014-8091 affects the X.Org X Window System and X11R5 implementations, specifically within the xserver component that handles SUN-DES-1 (Secure RPC) authentication mechanisms. This flaw exists in versions prior to 1.16.3 and represents a critical security issue that undermines the stability and availability of graphical display servers. The vulnerability stems from inadequate error handling within the memory allocation process, creating a path for remote attackers to exploit the system through carefully crafted connection requests.
The technical root cause of this vulnerability lies in the improper validation of memory allocation return values during the authentication process. When the X server processes connection requests using SUN-DES-1 authentication, it attempts to allocate memory for credential handling through malloc calls. The flaw occurs when the system fails to verify whether the malloc operation successfully allocated memory, allowing execution to continue with a NULL pointer reference. This particular weakness maps directly to CWE-476, which describes NULL pointer dereference conditions that can lead to system crashes and denial of service scenarios.
The operational impact of this vulnerability is significant for systems relying on X Window System for graphical interfaces, particularly in enterprise environments where display servers handle multiple concurrent connections. Remote attackers can exploit this weakness by sending specially crafted connection requests that trigger the faulty memory allocation path, resulting in immediate server crashes and complete denial of service for legitimate users. The vulnerability affects both the traditional X11R5 implementation and the modern X.Org Server, indicating a widespread issue within the X Window System ecosystem that has persisted across multiple generations of the software.
This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks targeting services and systems. The attack vector allows for remote exploitation without requiring authentication or elevated privileges, making it particularly dangerous for publicly accessible systems. The memory corruption aspect of this vulnerability also relates to broader concepts of heap management and memory safety that are fundamental to secure system operation. Organizations using affected X Window System implementations face potential disruption of graphical user interfaces, application availability, and overall system stability, particularly in multi-user environments where display servers manage numerous concurrent sessions.
The recommended mitigation strategy involves immediate deployment of X.Org Server version 1.16.3 or later, which includes proper error checking for malloc return values. System administrators should also implement network segmentation to limit exposure of X server components to untrusted networks, and consider disabling SUN-DES-1 authentication where it is not strictly required. Additionally, monitoring for unusual connection patterns and implementing intrusion detection systems can help identify exploitation attempts before they cause service disruption. The fix demonstrates the critical importance of proper error handling in security-sensitive code paths and serves as a reminder of the need for comprehensive memory safety practices in system-level software development.