CVE-2011-3050 in iOS
Summary
by MITRE
Use-after-free vulnerability in the Cascading Style Sheets (CSS) implementation in Google Chrome before 17.0.963.83 allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors related to the :first-letter pseudo-element.
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Analysis
by VulDB Data Team • 04/13/2021
The vulnerability identified as CVE-2011-3050 represents a critical use-after-free flaw within Google Chrome's CSS implementation that existed prior to version 17.0.963.83. This type of vulnerability occurs when a program continues to reference memory locations that have already been freed, creating opportunities for malicious exploitation that can result in system instability or arbitrary code execution. The specific context of this vulnerability involves the handling of the :first-letter pseudo-element in CSS, which is a selector used to style the first letter of a text element, making it a common feature in web page styling and typography.
The technical implementation of this vulnerability stems from improper memory management within Chrome's rendering engine when processing CSS rules that involve the :first-letter pseudo-element. When a web page contains CSS declarations that utilize this pseudo-element, Chrome's parser and rendering components may not properly track the lifecycle of memory objects associated with these CSS properties. The flaw manifests when the browser processes dynamic updates to elements that use :first-letter styling, potentially causing memory to be freed while still referenced by other components in the rendering pipeline. This memory corruption scenario creates a condition where attackers can manipulate the browser's memory state to execute malicious code or cause the application to crash.
The operational impact of CVE-2011-3050 extends beyond simple denial of service to potentially enable remote code execution in certain circumstances. Attackers can craft malicious web pages that trigger the vulnerable code path through carefully constructed CSS rules that reference the :first-letter pseudo-element. When users visit these malicious sites, the browser's rendering engine encounters the malformed CSS and attempts to free memory that is subsequently accessed, creating opportunities for exploitation. This vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions, and can be mapped to ATT&CK technique T1059.001 for command and scripting interpreter usage, as successful exploitation could allow attackers to execute arbitrary commands on affected systems.
Mitigation strategies for this vulnerability require immediate patching of affected Chrome versions to the fixed release 17.0.963.83 or later, which addresses the memory management issues in the CSS parser. Organizations should implement browser hardening measures including disabling unnecessary CSS features, employing content security policies, and maintaining up-to-date browser versions through automated patch management systems. Additionally, network-level protections such as web application firewalls and browser sandboxing can provide defense-in-depth measures. The vulnerability demonstrates the importance of proper memory management in browser rendering engines and highlights the need for comprehensive testing of CSS implementations against memory safety vulnerabilities. Security teams should also monitor for similar patterns in other browser components and ensure that all web rendering engines undergo regular security assessments to identify and remediate use-after-free conditions before they can be exploited in the wild.