CVE-2011-3105 in iOS
Summary
by MITRE
Use-after-free vulnerability in the Cascading Style Sheets (CSS) implementation in Google Chrome before 19.0.1084.52 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-2011-3105 represents a critical use-after-free flaw within Google Chrome's CSS implementation that existed prior to version 19.0.1084.52. This type of vulnerability occurs when a program continues to reference memory that has already been freed, creating a dangerous condition that can be exploited by malicious actors. The specific weakness manifests within the handling of the :first-letter pseudo-element, a CSS feature that applies styling to the first letter of a text element, making it particularly insidious as it leverages standard web styling mechanisms to execute attacks.
The technical exploitation of this vulnerability involves crafting malicious web content that triggers the CSS parser to create a use-after-free condition when processing the :first-letter pseudo-element. When Chrome's rendering engine encounters such malformed CSS input, it may free memory associated with CSS style objects while still maintaining references to them, leading to unpredictable behavior. This condition can be triggered through various vectors including malformed HTML documents, CSS files, or dynamically generated content that manipulates the :first-letter pseudo-element in unexpected ways. The vulnerability's classification as a use-after-free aligns with CWE-416, which specifically addresses the reuse of freed memory, a well-documented and dangerous class of memory safety issues.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable more severe consequences including arbitrary code execution. When an attacker successfully triggers the use-after-free condition, the browser may crash or become unstable, resulting in a denial of service that disrupts legitimate user activities. However, the more concerning aspect is that such memory corruption vulnerabilities often provide attackers with opportunities to execute malicious code within the browser's security context, potentially leading to complete system compromise. The vulnerability affects not just individual users but could be leveraged in targeted attacks against specific victims or broader campaigns exploiting the widespread use of Chrome as a web browser.
Mitigation strategies for CVE-2011-3105 primarily involve upgrading to Google Chrome version 19.0.1084.52 or later, which contains the necessary patches to address the memory management issues in the CSS parser. Additionally, users should maintain awareness of the potential for malicious websites to exploit such vulnerabilities and employ standard security practices including keeping software updated, using browser security features, and avoiding untrusted content. Organizations should implement network monitoring to detect potential exploitation attempts and ensure that their security policies include regular browser updates as part of their vulnerability management procedures. The ATT&CK framework categorizes this type of vulnerability under T1211 - Exploitation for Defense Evasion and T1059 - Command and Scripting Interpreter, highlighting the broader threat landscape that such memory corruption vulnerabilities represent in modern attack chains.