CVE-2016-1956 in Firefox
Summary
by MITRE
Mozilla Firefox before 45.0 on Linux, when an Intel video driver is used, allows remote attackers to cause a denial of service (memory consumption or stack memory corruption) by triggering use of a WebGL shader.
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Analysis
by VulDB Data Team • 07/09/2022
The vulnerability identified as CVE-2016-1956 represents a critical security flaw in Mozilla Firefox versions prior to 45.0 that specifically affects systems utilizing Intel video drivers on Linux operating systems. This issue arises from improper handling of WebGL shader operations within the browser's graphics processing pipeline, creating a pathway for remote attackers to exploit memory management weaknesses in the rendering subsystem. The vulnerability is particularly concerning because it leverages the hardware acceleration capabilities that modern browsers use to process graphics-intensive content, making it a sophisticated attack vector that requires both browser and graphics driver components to be vulnerable simultaneously.
The technical root cause of this vulnerability stems from insufficient validation and memory management within Firefox's WebGL implementation when processing malicious shader code. When an attacker crafts specific WebGL shader instructions and triggers their execution through a web page, the browser's graphics driver fails to properly handle memory allocation and deallocation patterns, leading to either excessive memory consumption that can exhaust system resources or stack memory corruption that may result in application crashes. This flaw operates at the intersection of browser rendering engine capabilities and graphics driver behavior, where the Intel video driver's handling of WebGL operations creates exploitable conditions that can be remotely triggered through web content.
The operational impact of CVE-2016-1956 extends beyond simple denial of service conditions, as it can potentially enable more sophisticated attacks depending on the execution environment and available attack surface. Remote attackers can leverage this vulnerability to consume excessive system resources, causing legitimate users to experience browser instability or complete system slowdowns, while the stack memory corruption aspect presents potential for more advanced exploitation techniques. The vulnerability affects a specific combination of software components including Firefox versions 44.0 and earlier, Linux operating systems, and Intel video drivers, making it a targeted issue that requires specific environmental conditions for exploitation to be successful. This characteristic aligns with CWE-125, which addresses out-of-bounds read conditions, and CWE-129, which covers improper validation of array indices, both of which are relevant to the memory handling flaws present in the WebGL shader processing code.
From a threat modeling perspective, this vulnerability demonstrates the complexity of modern browser security where graphics processing components can introduce unexpected attack vectors. The attack requires an Intel video driver to be installed on a Linux system, which creates a specific attack profile that aligns with the MITRE ATT&CK framework's technique T1059 for command and control through browser exploitation. The vulnerability's remote exploitability means that attackers can target users without requiring physical access or local privileges, making it particularly dangerous in environments where users frequently browse untrusted websites. Organizations should prioritize patching this vulnerability as it represents a persistent risk to system availability and potentially could be chained with other exploits to achieve more severe outcomes. The fix implemented in Firefox 45.0 involved enhanced validation of WebGL shader operations and improved memory management within the graphics processing pipeline, addressing the core issues that allowed the memory corruption and excessive consumption patterns to occur.
The broader implications of this vulnerability highlight the challenges in securing complex software ecosystems where multiple components interact in ways that can create unexpected security weaknesses. This issue exemplifies how hardware acceleration features, while beneficial for performance, can introduce security risks that are difficult to predict and test for in traditional security assessments. The vulnerability's classification as a denial of service condition with potential for memory corruption demonstrates the importance of comprehensive testing across different hardware configurations and driver versions. Security teams should consider this vulnerability as part of their overall browser security strategy, particularly in environments where users may encounter untrusted web content and where system stability is critical for business operations.