CVE-2016-7945 in libXi
Summary
by MITRE
Multiple integer overflows in X.org libXi before 1.7.7 allow remote X servers to cause a denial of service (out-of-bounds memory access or infinite loop) via vectors involving length fields.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2016-7945 represents a critical security flaw within the X.org libXi library version 1.7.6 and earlier, which serves as a core component in the X Window System for handling input device events. This issue stems from multiple integer overflow conditions that occur when processing length fields in X protocol messages, creating a pathway for remote attackers to manipulate the library's behavior. The affected library is widely deployed across Unix-like operating systems and serves as a fundamental building block for graphical user interfaces, making the impact of this vulnerability particularly significant. Integer overflows in this context occur when arithmetic operations produce results that exceed the maximum value representable by the data type, leading to unexpected behavior in the program's execution flow.
The technical exploitation of this vulnerability involves remote X servers sending specially crafted protocol messages containing malformed length fields that trigger integer overflow conditions within the libXi library. When these overflow conditions occur, they can result in out-of-bounds memory access patterns or infinite loop scenarios that ultimately lead to denial of service conditions. The vulnerability manifests through the library's failure to properly validate input data lengths before performing operations that depend on these values, creating a scenario where legitimate input can be manipulated to cause memory corruption or resource exhaustion. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is classified as a common weakness in software security practices. The X protocol's design allows for remote servers to communicate with client applications through the X11 forwarding mechanism, providing attackers with a clear attack surface through which they can exploit these integer overflows.
The operational impact of CVE-2016-7945 extends beyond simple denial of service, as it can potentially enable more sophisticated attacks depending on the system configuration and execution environment. When exploited successfully, the vulnerability can cause applications using libXi to crash or enter infinite loop states, effectively rendering input handling functionality unusable. This affects not only the targeted application but can also impact the entire graphical session, as libXi is integral to input device management across the X Window System. The vulnerability's remote nature means that attackers do not require local system access to exploit it, making it particularly dangerous in networked environments where X11 forwarding is enabled. Systems running vulnerable versions of libXi are at risk of being rendered unusable through simple network-based attacks, which can be particularly problematic in enterprise environments where graphical interfaces are heavily utilized. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique of Network Denial of Service, as it specifically targets network-based services to cause operational disruption. Additionally, the vulnerability could potentially be leveraged as a stepping stone for more complex attacks, especially when combined with other exploitation techniques that might be available in the same environment.
Mitigation strategies for CVE-2016-7945 primarily involve upgrading to libXi version 1.7.7 or later, which contains the necessary patches to address the integer overflow conditions. System administrators should prioritize patching affected systems, particularly those that expose X11 services to untrusted networks or users. In environments where immediate patching is not feasible, network-level mitigations can be implemented through firewall rules that restrict X11 traffic or disable X11 forwarding where possible. The vulnerability demonstrates the importance of input validation in security-critical libraries and highlights the need for comprehensive testing of arithmetic operations within protocol implementations. Organizations should implement regular vulnerability scanning procedures to identify and remediate similar issues in their software supply chains, as integer overflows remain a persistent threat in software development practices. The patch for this vulnerability specifically addresses the validation of length fields in X protocol messages, ensuring that integer arithmetic operations are properly bounded and that overflow conditions are detected and handled gracefully. This represents a fundamental security improvement that prevents malicious actors from leveraging these conditions to disrupt system operations or potentially escalate privileges through more complex attack vectors.