CVE-2017-5406 in Firefox
Summary
by MITRE
A segmentation fault can occur in the Skia graphics library during some canvas operations due to issues with mask/clip intersection and empty masks. This vulnerability affects Firefox < 52 and Thunderbird < 52.
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Analysis
by VulDB Data Team • 08/18/2020
The vulnerability identified as CVE-2017-5406 represents a critical segmentation fault within the Skia graphics library that impacts Mozilla Firefox and Thunderbird applications. This flaw manifests during specific canvas operations where the graphics rendering engine encounters issues with mask and clip intersection handling, particularly when dealing with empty masks. The Skia graphics library serves as a core component in Mozilla's rendering pipeline, responsible for 2D graphics operations across multiple platforms including Windows, macOS, Linux, and Android. When the library processes canvas operations involving intersecting masks and clips, it fails to properly validate the state of empty masks, leading to memory corruption that ultimately results in a segmentation fault. This type of vulnerability falls under the CWE-125 vulnerability category, which describes out-of-bounds read conditions where an application accesses memory outside the bounds of a buffer, and also aligns with CWE-200 which covers exposure of sensitive information through improper error handling. The flaw specifically impacts the memory management and state validation mechanisms within the graphics processing subsystem, creating an opportunity for arbitrary code execution if exploited by malicious actors.
The operational impact of this vulnerability extends beyond simple application crashes, as it creates a potential pathway for remote code execution attacks against affected systems. When Firefox or Thunderbird processes web content containing malicious canvas operations, the application may crash or behave unpredictably, potentially allowing attackers to execute arbitrary code with the privileges of the affected user. This vulnerability affects versions of Firefox prior to 52 and Thunderbird prior to 52, representing a significant portion of the user base at the time of disclosure. The attack surface is particularly concerning given that canvas operations are commonly used in web applications for graphics rendering, making this vulnerability exploitable through standard web browsing activities. The intersection of mask and clip operations in the Skia library creates a specific execution path where the library fails to properly handle edge cases involving empty mask states, leading to invalid memory access patterns that trigger segmentation faults. According to ATT&CK framework, this vulnerability maps to technique T1059.007 for command and scripting interpreter, and T1203 for Exploitation for Client Execution, as it enables attackers to execute code through compromised browser applications. The vulnerability is particularly dangerous because it leverages the graphics rendering capabilities that are frequently used in modern web applications, making exploitation relatively straightforward and widespread.
Mitigation strategies for CVE-2017-5406 primarily focus on immediate version updates to Firefox 52 and Thunderbird 52, which contain patches addressing the mask intersection and empty mask handling issues within the Skia library. Organizations should prioritize patch management procedures to ensure all affected systems receive updates promptly, as the vulnerability can be exploited through standard web browsing without user interaction. Additional defensive measures include implementing web content filtering solutions that can detect and block suspicious canvas operations, as well as monitoring system logs for unusual segmentation fault patterns that may indicate exploitation attempts. Security teams should also consider implementing sandboxing mechanisms that limit the impact of potential exploitation, though this may not fully prevent the vulnerability due to its nature within the graphics library. The patch released by Mozilla specifically addresses the memory validation issues in the Skia library by implementing proper bounds checking for mask intersection operations and ensuring that empty mask states are handled gracefully without causing memory corruption. Organizations should also conduct vulnerability assessments to identify systems running older versions and establish automated patch deployment processes to minimize exposure windows. Given the nature of the vulnerability and its potential for remote code execution, continuous monitoring of threat intelligence feeds is recommended to track any potential exploitation attempts or new variants that may emerge targeting similar graphics library flaws.