CVE-2011-3021 in iOS
Summary
by MITRE
Use-after-free vulnerability in Google Chrome before 17.0.963.56 allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors related to subframe loading.
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Analysis
by VulDB Data Team • 04/13/2021
The vulnerability identified as CVE-2011-3021 represents a critical use-after-free flaw in Google Chrome browser versions prior to 17.0.963.56. 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 flaw specifically manifests during subframe loading operations, which are integral components of web page rendering where multiple frames or iframes are processed within a single webpage context. The vulnerability's classification as a use-after-free aligns with CWE-416, which defines the improper deallocation of memory resources as a fundamental weakness in software security architecture.
The technical exploitation of this vulnerability occurs when Chrome processes subframes, particularly during the dynamic loading and unloading of frame content. When a subframe is destroyed or removed from memory, the browser's memory management system frees the associated resources. However, in vulnerable versions, Chrome fails to properly invalidate references to these freed memory locations, allowing attackers to manipulate the browser's memory state through carefully crafted web content. This manipulation can occur through maliciously constructed web pages that trigger the specific sequence of events leading to the use-after-free condition. The attack vector is particularly insidious because it operates entirely within the browser's rendering engine, requiring no special privileges or user interaction beyond visiting a malicious website.
The operational impact of CVE-2011-3021 extends beyond simple denial of service scenarios, as the vulnerability may enable more severe consequences including arbitrary code execution. When a use-after-free condition is successfully exploited, attackers can potentially overwrite critical memory locations with malicious code, effectively taking control of the browser process. This represents a significant threat to user security since browsers handle sensitive data and execute code from multiple sources simultaneously. The vulnerability's presence in Chrome versions prior to 17.0.963.56 meant that millions of users were potentially exposed to remote exploitation, with the attack surface expanding to include any website that might trigger the problematic subframe loading behavior. The exploitability of this vulnerability aligns with ATT&CK technique T1059, which covers the execution of malicious code through browser-based attacks, and T1211, which addresses the exploitation of memory corruption vulnerabilities.
Mitigation strategies for CVE-2011-3021 primarily involve immediate browser updates to versions 17.0.963.56 or later, where Google has implemented proper memory management fixes. Organizations should prioritize patch management and ensure all users have updated their Chrome installations to prevent exploitation. Additionally, network administrators can implement web filtering solutions that block access to known malicious domains, though this approach provides only partial protection since the vulnerability can be exploited through legitimate websites that trigger the problematic code path. The remediation process should also include user education about avoiding untrusted websites and maintaining updated software versions. From a defensive perspective, this vulnerability demonstrates the importance of robust memory safety practices in browser development and highlights the need for continuous security testing and code review processes to identify and prevent similar memory corruption issues. The fix implemented by Google involved strengthening the memory management routines during subframe operations and ensuring proper invalidation of references when frame content is destroyed, addressing the root cause of the use-after-free condition as defined by CWE-416 standards.