CVE-2013-1995 in libXi
Summary
by MITRE
X.org libXi 1.7.1 and earlier allows X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to an unexpected sign extension in the XListInputDevices function.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability identified as CVE-2013-1995 affects X.org libXi version 1.7.1 and earlier, representing a critical memory safety issue within the X Window System input device management subsystem. This flaw manifests in the XListInputDevices function where improper handling of data types leads to unexpected behavior during memory allocation operations. The vulnerability stems from a sign extension issue that occurs when processing input device information, creating conditions where malicious X servers can manipulate memory allocation parameters to trigger buffer overflow conditions. Such flaws are particularly dangerous in graphical environments where multiple X servers may interact with the same input device management infrastructure.
The technical implementation of this vulnerability involves a specific code path within the XListInputDevices function where integer values undergo unexpected sign extension operations. When processing input device lists, the system fails to properly validate or constrain integer values that are subsequently used for memory allocation calculations. This creates a scenario where an attacker-controlled value can cause the system to allocate insufficient memory space, followed by a subsequent buffer overflow when attempting to write data beyond the allocated boundaries. The flaw is categorized under CWE-129 as an "Improper Validation of Array Index" and also relates to CWE-121 as "Stack-based Buffer Overflow" due to the buffer overflow conditions that can be triggered. The vulnerability represents a classic example of how improper integer handling can lead to memory corruption issues in systems managing graphical input devices.
The operational impact of CVE-2013-1995 extends beyond simple denial of service conditions to potentially enable arbitrary code execution within the context of the X server process. Attackers can exploit this vulnerability by establishing a malicious X server connection and manipulating input device information to force memory allocation failures and subsequent buffer overflows. This could allow for privilege escalation attacks, particularly when the X server process runs with elevated privileges. The vulnerability affects systems using X.org libXi libraries, which are prevalent in Linux desktop environments, X Window System implementations, and various graphical user interface frameworks. Systems that rely on multiple X servers or have complex input device configurations are particularly susceptible to exploitation. The ATT&CK framework categorizes this vulnerability under T1068 as "Exploitation for Privilege Escalation" and T1059 as "Command and Scripting Interpreter" since exploitation typically requires crafting specific input sequences that can be interpreted by the vulnerable X server implementation.
Mitigation strategies for CVE-2013-1995 involve immediate patching of affected X.org libXi libraries to versions that properly validate integer values and prevent sign extension issues in memory allocation calculations. System administrators should prioritize updating X server implementations and ensuring that all input device handling code properly validates input parameters before using them in memory allocation contexts. Additional defensive measures include implementing network segmentation to limit access to X server interfaces, employing privilege separation techniques to reduce the impact of potential exploitation, and monitoring for unusual memory allocation patterns or buffer overflow indicators. The vulnerability highlights the importance of proper integer type handling in systems managing graphical input devices and demonstrates how seemingly minor implementation flaws can create significant security risks in desktop computing environments. Organizations should also consider implementing runtime protection mechanisms such as address space layout randomization and stack canaries to provide additional defense-in-depth against exploitation attempts.