CVE-2015-4497 in Firefox
Summary
by MITRE
Use-after-free vulnerability in the CanvasRenderingContext2D implementation in Mozilla Firefox before 40.0.3 and Firefox ESR 38.x before 38.2.1 allows remote attackers to execute arbitrary code by leveraging improper interaction between resize events and changes to Cascading Style Sheets (CSS) token sequences for a CANVAS element.
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Analysis
by VulDB Data Team • 10/22/2024
The vulnerability CVE-2015-4497 represents a critical use-after-free flaw within Mozilla Firefox's CanvasRenderingContext2D implementation, affecting versions prior to 40.0.3 and Firefox ESR 38.x prior to 38.2.1. This security issue stems from improper handling of interactions between resize events and CSS token sequence modifications for canvas elements, creating a scenario where memory that has been freed is still accessed by the application. The flaw operates at the intersection of web rendering and memory management, where the browser's canvas rendering context fails to properly validate memory references during dynamic element modifications. According to CWE-416, this vulnerability specifically manifests as a use-after-free condition, where the application continues to reference memory locations that have already been deallocated, potentially leading to memory corruption and arbitrary code execution.
The technical exploitation of this vulnerability requires a remote attacker to craft malicious web content that triggers a sequence of events involving canvas element resizing and concurrent CSS modifications. When a canvas element undergoes a resize operation while CSS token sequences are being modified, the CanvasRenderingContext2D implementation fails to properly synchronize these operations, resulting in a race condition that leads to memory corruption. The attacker can leverage this condition to execute arbitrary code with the privileges of the victim user, making it particularly dangerous in web browsing environments where users encounter untrusted content. The vulnerability's impact is amplified by its ability to be triggered through standard web page rendering processes, requiring no special user interaction beyond visiting a malicious website.
From an operational perspective, this vulnerability poses significant risks to organizations relying on Firefox for web browsing, as it can be exploited through drive-by downloads or malicious websites without requiring user consent or interaction. The attack surface is broad since canvas elements are commonly used in web applications for graphics rendering, data visualization, and interactive content. The memory corruption resulting from this use-after-free condition can lead to various exploitation outcomes including privilege escalation, information disclosure, or complete system compromise depending on the execution environment and available mitigations. Organizations using affected Firefox versions face potential data breaches, system compromise, and unauthorized access to sensitive information through this remote code execution vulnerability.
Mitigation strategies for CVE-2015-4497 primarily focus on immediate patching of affected Firefox installations to versions 40.0.3 or later for regular releases, and 38.2.1 for ESR versions. Security administrators should implement comprehensive browser update policies to ensure all systems are running patched versions. Additional protective measures include deploying web application firewalls, implementing content security policies, and configuring browser security settings to limit canvas element usage where possible. The vulnerability aligns with ATT&CK technique T1059.007 for command and script interpreter execution, as successful exploitation could lead to arbitrary code execution within the browser context. Organizations should also consider implementing browser isolation techniques and monitoring for suspicious canvas element behaviors to detect potential exploitation attempts. Regular security assessments and vulnerability scanning should include checks for affected Firefox versions to prevent exploitation of this use-after-free condition.