CVE-2013-2003 in libXcursor
Summary
by MITRE
Integer overflow in X.org libXcursor 1.1.13 and earlier allows X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the _XcursorFileHeaderCreate function.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability identified as CVE-2013-2003 represents a critical integer overflow flaw within the X.org libXcursor library version 1.1.13 and earlier implementations. This security issue specifically affects the _XcursorFileHeaderCreate function which handles cursor file processing within X Window System environments. The flaw arises from improper handling of integer arithmetic operations that can lead to miscalculations in memory allocation sizes, creating conditions where insufficient memory is allocated for cursor data structures. This vulnerability exists within the X Window System ecosystem which serves as the foundational graphical interface framework for numerous Unix-like operating systems including various linux distributions and BSD variants. The affected library is widely deployed across desktop environments, server configurations, and embedded systems that rely on X11 graphical protocols for user interface rendering and interaction.
The technical exploitation of this vulnerability occurs when malicious X servers or applications process cursor files that contain crafted integer values within their headers. During the _XcursorFileHeaderCreate function execution, the library performs calculations to determine the appropriate memory allocation size for cursor data structures. When integer overflow occurs, the calculated size becomes smaller than the actual data requirements, leading to insufficient memory allocation. This memory miscalculation results in buffer overflow conditions where subsequent data writes overwrite adjacent memory regions. The vulnerability falls under CWE-190, which specifically addresses integer overflow conditions, and represents a classic example of improper integer handling that can lead to arbitrary code execution. The flaw is particularly dangerous because it can be triggered through legitimate cursor file processing operations, making it difficult to distinguish between benign and malicious input data.
The operational impact of CVE-2013-2003 extends beyond simple memory corruption, presenting significant security risks to systems running affected X.org implementations. An attacker could potentially leverage this vulnerability to execute arbitrary code within the context of the X server process, which typically runs with elevated privileges in graphical environments. This could lead to complete system compromise, privilege escalation, or denial of service conditions that disrupt graphical user interfaces and desktop environments. The vulnerability affects systems where X11 servers process untrusted cursor data, including remote desktop connections, X server implementations in virtualized environments, and applications that handle cursor files from external sources. The attack surface is broad given that X.org libXcursor is a fundamental component of most Unix-like graphical systems, making this vulnerability particularly concerning for enterprise environments and server deployments that utilize X11 protocols.
Mitigation strategies for CVE-2013-2003 focus primarily on updating to patched versions of the X.org libXcursor library, with version 1.1.14 and later containing the necessary fixes for integer overflow handling. System administrators should implement comprehensive patch management procedures to ensure all X Window System components are updated promptly. Additional protective measures include implementing input validation for cursor files, restricting X server access to trusted sources, and employing network segmentation to limit exposure to potentially malicious X server connections. Security monitoring should focus on detecting unusual memory allocation patterns and buffer overflow indicators within X server processes. Organizations should also consider implementing runtime protections such as stack canaries, address space layout randomization, and heap-based memory protection mechanisms to reduce the exploitability of similar vulnerabilities. The ATT&CK framework categorizes this vulnerability under privilege escalation and code execution techniques, emphasizing the need for layered security approaches that address both the specific vulnerability and broader system security posture.