CVE-2013-1992 in libdmx
Summary
by MITRE
Multiple integer overflows in X.org libdmx 1.1.2 and earlier allow X servers to trigger allocation of insufficient memory and a buffer overflow via vectors related to the (1) DMXGetScreenAttributes, (2) DMXGetWindowAttributes, and (3) DMXGetInputAttributes functions.
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Analysis
by VulDB Data Team • 05/14/2021
The vulnerability identified as CVE-2013-1992 represents a critical security flaw within the X.org libdmx library version 1.1.2 and earlier implementations. This issue affects the distributed multihead X server functionality that enables multiple displays to be managed through a single X server instance. The vulnerability stems from improper input validation in three specific functions: DMXGetScreenAttributes, DMXGetWindowAttributes, and DMXGetInputAttributes, which are integral to the distributed X server management system. These functions handle attribute queries for screen, window, and input device configurations respectively, making them critical components in multi-display environments.
The technical flaw manifests as integer overflows that occur when processing certain attribute requests within the DMX protocol implementation. When malicious X servers send crafted requests containing oversized attribute values, the integer overflow conditions cause the system to allocate insufficient memory buffers before performing the actual memory allocation. This memory allocation failure creates a buffer overflow condition that can be exploited to overwrite adjacent memory locations. The vulnerability is particularly dangerous because it allows remote attackers to manipulate the X server's memory management routines through legitimate protocol interactions, effectively bypassing normal access controls and memory protection mechanisms.
The operational impact of this vulnerability extends beyond simple memory corruption, as it can lead to arbitrary code execution within the X server process. Attackers can leverage this weakness to gain elevated privileges and potentially compromise the entire graphical session. The vulnerability affects systems running X.org libdmx versions prior to 1.1.3, making it relevant to a broad range of Unix-like systems including Linux distributions and other operating systems that utilize the X Window System for graphical user interfaces. The attack vector requires only network access to the X server, making it particularly dangerous in multi-user environments or when X servers are configured to accept remote connections.
This vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and CWE-121, Stack-based Buffer Overflow, which are fundamental weaknesses in memory safety and input validation. From an ATT&CK framework perspective, this issue maps to T1068, Exploitation for Privilege Escalation, and T1059, Command and Scripting Interpreter, as attackers can leverage the buffer overflow to execute malicious code. The vulnerability also relates to T1203, Exploitation of Remote Services, since it exploits network-accessible X server functionality. Organizations using distributed X server configurations are particularly at risk, as the vulnerability can be exploited by remote attackers without requiring physical access to the system. The memory corruption resulting from this integer overflow can lead to system instability, crashes, or complete system compromise, making it a high-priority vulnerability for immediate remediation.
The recommended mitigation strategy involves upgrading to libdmx version 1.1.3 or later, which contains the necessary patches to address the integer overflow conditions in the affected functions. System administrators should also implement proper network segmentation to limit access to X servers and disable unnecessary X11 forwarding capabilities. Additionally, monitoring network traffic for unusual X server attribute requests can help detect potential exploitation attempts. The vulnerability demonstrates the importance of thorough input validation in network-facing protocols and highlights the risks associated with legacy X server implementations that may not receive regular security updates. Organizations should also consider implementing privilege separation mechanisms and restricting X server access to trusted network segments to minimize the potential impact of such vulnerabilities.