CVE-2012-2818 in iOS
Summary
by MITRE
Use-after-free vulnerability in Google Chrome before 20.0.1132.43 allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors related to the layout of documents that use the Cascading Style Sheets (CSS) counters feature.
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Analysis
by VulDB Data Team • 04/13/2021
The CVE-2012-2818 vulnerability represents a critical use-after-free flaw in Google Chrome browser versions prior to 20.0.1132.43, fundamentally compromising the browser's memory management integrity. This vulnerability specifically targets the CSS counters feature within the browser's document layout engine, creating a condition where freed memory blocks are accessed after being deallocated, potentially leading to arbitrary code execution or complete system compromise. The flaw exists in the way Chrome handles memory allocation and deallocation during the processing of CSS counter styles, which are used to automatically number elements in web documents such as headings, lists, or sections. When malicious web content triggers the processing of CSS counters in specific configurations, the browser's memory management system fails to properly track the lifecycle of allocated objects, resulting in a scenario where freed memory locations are accessed by subsequent operations.
The technical exploitation of this vulnerability requires remote attackers to craft malicious web pages that utilize CSS counter features in combination with specific document layouts that trigger the memory corruption condition. The attack vector leverages the browser's rendering engine's handling of CSS counter increment and reset operations, where the interaction between counter state management and document layout calculations creates opportunities for memory corruption. This use-after-free condition occurs when the browser's CSS counter implementation fails to properly synchronize access to counter state variables and their associated memory structures during document reflow operations. The vulnerability's impact extends beyond simple denial of service, as the memory corruption can potentially be leveraged for privilege escalation or arbitrary code execution within the browser sandbox, making it a significant threat to user security and system integrity.
The operational impact of CVE-2012-2818 is substantial given Chrome's widespread adoption and the vulnerability's potential for remote exploitation without user interaction. Organizations and individual users running affected Chrome versions face elevated risk of being compromised through drive-by downloads, malicious advertisements, or compromised websites that utilize the specific CSS counter attack patterns. The vulnerability's classification aligns with CWE-416, which specifically addresses use-after-free conditions in software systems, and represents a classic example of how modern browser security models can be undermined by subtle memory management flaws in complex rendering engines. Attackers can exploit this vulnerability through standard web browsing activities, making it particularly dangerous as it requires no specialized knowledge or physical access to target systems. The vulnerability's presence in Chrome's core rendering pipeline means that any website displaying content with CSS counters could potentially serve as an attack vector, significantly expanding the attack surface.
Mitigation strategies for CVE-2012-2818 primarily focus on immediate browser updates to versions 20.0.1132.43 or later, which contain patches addressing the memory management issues in the CSS counter implementation. System administrators should implement comprehensive patch management procedures to ensure all Chrome installations are updated promptly, as the vulnerability affects all operating systems where Chrome is deployed. Additional protective measures include implementing web content filtering solutions that can block access to known malicious sites, deploying browser security extensions that enhance memory protection mechanisms, and establishing monitoring procedures to detect potential exploitation attempts. The vulnerability's remediation aligns with ATT&CK technique T1059.007, which covers the use of web shells and browser-based attack vectors, emphasizing the importance of keeping browser components current. Organizations should also consider implementing sandboxing technologies and privilege separation mechanisms to limit the potential impact of successful exploitation attempts, while maintaining regular security assessments to identify similar memory corruption vulnerabilities in other browser components or web applications.