CVE-2013-1985 in libXinerama
Summary
by MITRE
Integer overflow in X.org libXinerama 1.1.2 and earlier allows X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the XineramaQueryScreens function.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability identified as CVE-2013-1985 represents a critical integer overflow flaw within the X.org libXinerama library version 1.1.2 and earlier implementations. This issue specifically affects the XineramaQueryScreens function which is responsible for querying screen configuration information in X Window System environments. The vulnerability stems from improper input validation and arithmetic handling within the memory allocation routines that process screen geometry data. When an X server processes certain malformed screen configuration parameters, the integer overflow condition causes the system to allocate insufficient memory buffers, leading to subsequent buffer overflow conditions during data processing operations. The flaw exists at the intersection of memory management and input validation, creating a scenario where malicious or malformed X server requests can trigger exploitable conditions.
The technical execution of this vulnerability involves an attacker manipulating the XineramaQueryScreens function with carefully crafted parameters that cause integer arithmetic to exceed the maximum representable value for the data type used in memory allocation calculations. This overflow results in a situation where the system allocates a buffer that is significantly smaller than required for the actual data processing, creating a classic buffer overflow condition. The vulnerability is classified under CWE-190 as an integer overflow or wraparound, and specifically relates to CWE-129 as an insufficient validation of array index. When the application attempts to write data beyond the allocated buffer boundaries, it can overwrite adjacent memory regions, potentially leading to arbitrary code execution or denial of service conditions.
The operational impact of CVE-2013-1985 extends across multiple X Window System implementations and affects any system running vulnerable versions of libXinerama. Attackers can exploit this vulnerability by establishing an X server connection and sending specially crafted XineramaQueryScreens requests that trigger the integer overflow condition. The attack surface includes desktop environments, remote desktop solutions, and any application that relies on X11 for graphical display operations. This vulnerability can be leveraged to achieve privilege escalation in certain scenarios where X server processes run with elevated permissions, or to cause system instability through denial of service conditions. The attack vector aligns with ATT&CK technique T1068 which involves local privilege escalation through exploitation of system vulnerabilities, and T1499 which covers network denial of service attacks targeting graphical subsystems.
Mitigation strategies for this vulnerability require immediate patching of affected libXinerama libraries to versions that properly handle integer overflow conditions in memory allocation calculations. System administrators should ensure that all X Window System components are updated to patched versions, particularly focusing on the libXinerama library which is the primary affected component. Additional protective measures include implementing network segmentation to limit X server access, disabling unnecessary X11 forwarding capabilities, and monitoring for suspicious X server connection patterns. The vulnerability demonstrates the importance of proper input validation and memory management practices in graphical system components, with recommendations aligning with security best practices outlined in NIST SP 800-128 for secure coding practices and the CWE top 25 most dangerous software weaknesses. Organizations should also consider implementing intrusion detection systems that can identify unusual X server activity patterns and maintain up-to-date vulnerability management processes to prevent exploitation of similar integer overflow conditions in other system components.