CVE-2016-7947 in libXrandr
Summary
by MITRE
Multiple integer overflows in X.org libXrandr before 1.5.1 allow remote X servers to trigger out-of-bounds write operations via a crafted response.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability identified as CVE-2016-7947 represents a critical security flaw within the X.org libXrandr library version 1.5.0 and earlier, which serves as a fundamental component for managing display configurations in X Window System environments. This issue stems from multiple integer overflow conditions that occur when processing X server responses, specifically affecting systems that utilize the X11 protocol for graphical user interface operations. The vulnerability exists in the way the library handles certain numerical values during display configuration operations, creating opportunities for malicious actors to manipulate memory structures through crafted X server responses.
The technical implementation of this vulnerability exploits integer overflow conditions that occur during the processing of display mode information and configuration parameters within the libXrandr library. When an X server sends a specially crafted response containing manipulated numerical values, the library fails to properly validate these inputs before performing arithmetic operations that result in integer overflows. These overflows subsequently lead to out-of-bounds write operations where malicious data can be written to memory locations outside the intended buffer boundaries. The flaw is particularly dangerous because it allows remote attackers to trigger these conditions without requiring local system access, making it exploitable over network connections. The vulnerability specifically affects the handling of display mode information, monitor configuration data, and other graphical configuration parameters that are commonly exchanged between X servers and client applications.
The operational impact of CVE-2016-7947 extends beyond simple denial of service scenarios, as the out-of-bounds write conditions can potentially lead to arbitrary code execution within the context of the affected application. Systems running vulnerable versions of libXrandr are at risk of being compromised when they process display configuration information from untrusted X servers, particularly in environments where users might connect to remote X sessions or when X11 forwarding is enabled in network services. The vulnerability affects a wide range of applications that depend on libXrandr for display management, including desktop environments, remote desktop solutions, and various graphical applications that utilize X11 protocols for their user interfaces. This makes the attack surface particularly broad across Unix-like systems and Linux distributions that rely on X Window System for their graphical capabilities.
The mitigation strategy for CVE-2016-7947 involves immediate upgrading of the libXrandr library to version 1.5.1 or later, which contains the necessary patches to address the integer overflow conditions. System administrators should also implement network segmentation and access controls to limit exposure to untrusted X servers, particularly in environments where X11 forwarding is enabled. Additionally, monitoring for suspicious X server activity and implementing proper input validation for display configuration data can help detect potential exploitation attempts. This vulnerability aligns with CWE-190, which describes integer overflow conditions, and can be mapped to ATT&CK technique T1059 for remote code execution through vulnerable system components. Organizations should also consider implementing security patches across all systems running affected versions of the X Window System and ensure that all network services utilizing X11 protocols are properly secured against unauthorized access.