CVE-2012-2118 in X11
Summary
by MITRE
Format string vulnerability in the LogVHdrMessageVerb function in os/log.c in X.Org X11 1.11 allows attackers to cause a denial of service or possibly execute arbitrary code via format string specifiers in an input device name.
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Analysis
by VulDB Data Team • 12/02/2021
The vulnerability identified as CVE-2012-2118 represents a critical format string vulnerability within the X.Org X11 server implementation, specifically within the LogVHdrMessageVerb function located in os/log.c. This flaw exists in X11 version 1.11 and demonstrates how improper input validation can lead to severe security implications in graphical server environments. The vulnerability stems from the function's handling of user-supplied input data that is directly incorporated into format string operations without proper sanitization, creating an attack surface that can be exploited by malicious actors.
The technical exploitation of this vulnerability occurs when an attacker provides a specially crafted input device name containing format string specifiers such as %s, %x, or %n. These specifiers, when processed by the vulnerable LogVHdrMessageVerb function, can cause the application to read from memory locations or write data to arbitrary addresses, potentially leading to stack corruption or memory overwrite conditions. The flaw is particularly dangerous because it operates within the core logging functionality of the X11 server, which is responsible for managing graphical input/output operations and device communications. This means that an attacker could leverage the vulnerability through legitimate device interaction mechanisms, making the attack vector both accessible and stealthy.
The operational impact of CVE-2012-2118 extends beyond simple denial of service conditions to encompass potential arbitrary code execution capabilities. When exploited successfully, this vulnerability allows attackers to manipulate the execution flow of the X11 server process, potentially leading to complete system compromise. The vulnerability affects the fundamental logging infrastructure of the X11 server, which processes messages from various input devices including keyboards, mice, and touchscreens. This makes the attack surface particularly broad since any device that communicates with the X11 server could serve as an exploitation vector, and the vulnerability can be triggered through normal device enumeration and interaction processes.
Security implications of this vulnerability align with CWE-134, which specifically addresses format string vulnerabilities where format strings are constructed from user-controlled data. The attack pattern follows typical exploit methodologies described in the MITRE ATT&CK framework under the T1059.007 technique for command and scripting interpreter, as the vulnerability enables attackers to execute arbitrary code through manipulated input processing. Organizations running affected X11 server versions face significant risk since the vulnerability can be exploited remotely through network-based device connections or locally through physical device manipulation, making it a particularly concerning issue for both desktop and server environments.
Mitigation strategies for CVE-2012-2118 require immediate patching of affected X11 server installations to the latest stable versions that contain proper input sanitization and format string handling. System administrators should implement input validation controls that prevent format specifiers from being processed within device name fields, and regular security audits should verify that all input processing functions properly sanitize user-supplied data. Additionally, network segmentation and access controls should be implemented to limit device access to trusted sources, while monitoring systems should be configured to detect anomalous device interaction patterns that may indicate exploitation attempts. The vulnerability serves as a critical reminder of the importance of proper input validation in server-side applications and the potential consequences of inadequate sanitization of user-controlled data in security-critical components.