CVE-2016-7951 in XRecord
Summary
by MITRE
Multiple integer overflows in X.org libXtst before 1.2.3 allow remote X servers to trigger out-of-bounds memory access operations by leveraging the lack of range checks.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2016-7951 affects X.org libXtst library versions prior to 1.2.3 and represents a critical integer overflow issue that can be exploited by remote X servers to cause out-of-bounds memory access operations. This flaw exists within the X Window System's X Test Extension library which provides testing capabilities for X servers including input simulation and screen capture functions. The vulnerability stems from insufficient range validation in integer variables used during memory allocation operations, creating opportunities for attackers to manipulate memory access patterns through crafted X protocol messages.
The technical implementation of this vulnerability involves multiple integer overflow conditions that occur when the libXtst library processes input from remote X servers without proper bounds checking. When an attacker sends specially crafted X protocol messages containing oversized integer values, these values can cause arithmetic operations to wrap around and produce incorrect memory allocation sizes. This results in memory buffers being allocated with insufficient space, leading to out-of-bounds writes that can corrupt adjacent memory regions. The flaw specifically impacts the XTest extension's ability to handle input events and screen capture operations, where integer variables control buffer sizes and iteration counts.
From an operational perspective, this vulnerability presents significant risks to systems running X Window System environments, particularly those accessible over networks where remote attackers could exploit the flaw. The impact extends beyond simple denial of service scenarios as the out-of-bounds memory access operations could potentially be leveraged for privilege escalation or code execution depending on the system configuration and memory layout. Systems utilizing X11 forwarding, remote desktop solutions, or any network-accessible X server implementations become vulnerable to this class of attack. The vulnerability affects not only desktop environments but also server configurations that rely on X11 for graphical interfaces and remote management capabilities.
The security implications align with CWE-190, which classifies integer overflow vulnerabilities, and can be mapped to ATT&CK technique T1059.007 for remote code execution through system services. Organizations should prioritize immediate patching of affected libXtst versions to prevent exploitation, while implementing network segmentation to limit exposure of X server services to untrusted networks. Additional mitigations include disabling unnecessary X11 features, implementing proper input validation for X protocol communications, and monitoring for unusual X server activity patterns. System administrators should also consider implementing network access controls and firewall rules to restrict X server access to trusted sources only. The vulnerability demonstrates the importance of proper integer validation in system libraries and highlights the need for comprehensive security testing of core infrastructure components that handle external input processing.