CVE-2011-3845 in Safari
Summary
by MITRE
Use-after-free vulnerability in Apple Safari 5.1.2, when a plug-in with a blocking function is installed, allows user-assisted remote attackers to execute arbitrary code via a crafted web page that is accessed during user interaction with the plug-in, leading to improper coordination between an API call and the plug-in unloading functionality, as demonstrated by the Adobe Flash and RealPlayer plug-ins.
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Analysis
by VulDB Data Team • 04/10/2017
The vulnerability described in CVE-2011-3845 represents a critical use-after-free condition affecting Apple Safari version 5.1.2 that demonstrates a fundamental flaw in memory management and plugin lifecycle coordination. This issue specifically manifests when Safari encounters web content that triggers interaction with certain third-party plugins, particularly those with blocking functions such as Adobe Flash and RealPlayer. The vulnerability operates through a sophisticated race condition where the browser's API call sequence fails to properly synchronize with the plugin unloading process, creating a temporal window where freed memory can be accessed and manipulated by malicious code.
The technical exploitation of this vulnerability relies on the improper coordination between Safari's JavaScript API calls and the dynamic loading/unloading of plugin components. When a user visits a crafted web page containing malicious content, the interaction with a blocking plugin triggers a sequence where the plugin's memory is freed while still being referenced by ongoing API calls. This creates a use-after-free condition that can be leveraged by remote attackers to execute arbitrary code with the privileges of the browser process. The vulnerability specifically targets the interaction between Safari's plugin architecture and the underlying memory management systems, exploiting a gap in how the browser handles plugin lifecycle events during user interaction scenarios.
From an operational perspective, this vulnerability presents a significant risk to users who regularly access web content that may contain malicious scripts or who have third-party plugins installed. The user-assisted nature of the attack means that exploitation requires some form of user interaction, typically through visiting a compromised website or clicking on malicious links. However, the impact is severe as successful exploitation can lead to complete system compromise, allowing attackers to execute arbitrary code, escalate privileges, and potentially gain persistent access to the affected system. The vulnerability affects a widely used browser and common plugins, making it particularly dangerous in real-world scenarios where users encounter diverse web content.
The security implications of CVE-2011-3845 align with CWE-416, which describes the use of freed memory condition, and can be mapped to ATT&CK technique T1059.007 for executing malicious code through web browsers. The vulnerability demonstrates poor input validation and memory management practices in the browser's plugin handling system, where the timing of API calls and plugin lifecycle events is not properly synchronized. Organizations should implement immediate mitigations including updating to patched versions of Safari, disabling unnecessary plugins, and implementing web content filtering solutions. The vulnerability also highlights the importance of proper memory management practices in browser security architectures, as it represents a classic example of how race conditions in plugin management can be exploited to achieve arbitrary code execution. Security teams should monitor for indicators of compromise related to this vulnerability and ensure that all browser and plugin components are kept current with security patches to prevent exploitation attempts.