CVE-2015-4512 in Firefox
Summary
by MITRE
gfx/2d/DataSurfaceHelpers.cpp in Mozilla Firefox before 41.0 on Linux improperly attempts to use the Cairo library with 32-bit color-depth surface creation followed by 16-bit color-depth surface display, which allows remote attackers to obtain sensitive information from process memory or cause a denial of service (out-of-bounds read) by using a CANVAS element to trigger 2D rendering.
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Analysis
by VulDB Data Team • 06/19/2022
The vulnerability identified as CVE-2015-4512 resides within the graphics rendering subsystem of Mozilla Firefox, specifically in the DataSurfaceHelpers.cpp file located in the gfx/2d directory. This flaw affects Firefox versions prior to 41.0 on Linux operating systems and represents a critical security issue that stems from improper handling of color depth specifications within the Cairo graphics library integration. The vulnerability manifests when the browser attempts to process canvas elements that trigger 2D rendering operations, creating a scenario where memory access patterns become exploitable.
The technical root cause of this vulnerability involves a mismatch between surface creation and display color depths within the Cairo graphics library. The implementation attempts to create 32-bit color-depth surfaces for rendering operations while simultaneously displaying content on 16-bit color-depth surfaces, creating a fundamental inconsistency in memory allocation and access patterns. This color depth mismatch occurs during the processing of canvas elements, where the graphics subsystem fails to properly validate or normalize the color depth specifications between the creation and display phases of surface operations.
The operational impact of this vulnerability extends beyond simple memory corruption to encompass both information disclosure and denial of service conditions. Remote attackers can exploit this flaw by crafting malicious web content that utilizes canvas elements to trigger the problematic rendering path, resulting in out-of-bounds memory reads that may expose sensitive process memory contents to attackers. The vulnerability's classification as a memory corruption issue aligns with CWE-125, which addresses out-of-bounds read conditions, while also potentially enabling privilege escalation scenarios through information leakage. Additionally, the implementation can cause denial of service conditions when the improper memory access patterns trigger application crashes or system instability.
This vulnerability demonstrates characteristics consistent with the attack pattern described in the MITRE ATT&CK framework under the technique of privilege escalation through memory corruption, where attackers leverage software flaws to gain unauthorized access to system resources. The specific exploitation pathway involves manipulating canvas rendering operations to force the graphics subsystem into an inconsistent state that exposes memory contents or causes system instability. The vulnerability's impact is particularly severe on Linux systems where the Cairo library integration is more susceptible to these color depth handling inconsistencies, making it a targeted concern for web-based attacks against Firefox installations.
The recommended mitigations for CVE-2015-4512 include immediate upgrading to Firefox version 41.0 or later, which contains the necessary patches to address the color depth handling inconsistencies in the Cairo library integration. System administrators should also implement network-level controls to restrict access to potentially malicious websites and consider deploying web application firewalls that can detect and block canvas-based exploitation attempts. The fix implemented in Firefox 41.0 addresses the core issue by ensuring proper validation of color depth specifications during surface creation and display operations, thereby preventing the out-of-bounds memory access patterns that enabled the vulnerability. Organizations should also conduct regular security assessments of their browser deployment environments to ensure all systems are updated with the latest security patches and maintain comprehensive monitoring for any suspicious activity related to graphics rendering operations.