CVE-2011-3957 in Chrome
Summary
by MITRE
Use-after-free vulnerability in the garbage-collection functionality in Google Chrome before 17.0.963.46 allows remote attackers to cause a denial of service or possibly have unspecified other impact via vectors involving PDF documents.
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Analysis
by VulDB Data Team • 03/20/2021
The vulnerability identified as CVE-2011-3957 represents a critical use-after-free condition within Google Chrome's garbage collection mechanism that existed in versions prior to 17.0.963.46. This flaw specifically manifests when processing PDF documents, making it particularly dangerous in web browsing environments where users frequently encounter PDF content. The issue stems from improper memory management during the automatic cleanup process, where freed memory blocks are still referenced by subsequent operations, creating exploitable conditions that can be leveraged by remote attackers. Such vulnerabilities fall under the broader category of memory corruption flaws that have been systematically catalogued by the Common Weakness Enumeration as CWE-416, which specifically addresses use-after-free conditions.
The technical exploitation of this vulnerability occurs when Chrome's garbage collector encounters certain PDF document structures that trigger an improper memory deallocation sequence. When a PDF object is freed from memory but references remain within the browser's memory management system, attackers can manipulate the PDF content to cause the freed memory to be reallocated and subsequently accessed, leading to unpredictable behavior. This particular flaw demonstrates how complex memory management systems in modern browsers can create attack surfaces when handling rich media content such as PDF documents. The garbage collection functionality in web browsers is designed to automatically manage memory allocation and deallocation, but this specific implementation contained a race condition or improper reference tracking that allowed malicious PDF content to exploit the system's memory management.
From an operational perspective, this vulnerability presents significant risks to users who browse the internet regularly, particularly in enterprise environments where PDF documents are commonly shared and opened within web browsers. The potential impact extends beyond simple denial of service to include unspecified other consequences that could potentially allow for arbitrary code execution or privilege escalation. Attackers could craft malicious PDF files that, when opened in vulnerable Chrome versions, would trigger the use-after-free condition and provide a means to execute malicious code on the target system. This represents a classic example of how browser-based vulnerabilities can be leveraged to achieve remote code execution, aligning with techniques documented in the MITRE ATT&CK framework under the T1059 category for command and scripting interpreters, as well as T1078 for valid accounts and T1203 for exploitation for privilege escalation.
The mitigation strategy for CVE-2011-3957 involves immediate upgrading to Google Chrome version 17.0.963.46 or later, which contains the patched garbage collection implementation that properly handles memory deallocation and reference tracking. Organizations should also implement comprehensive patch management procedures to ensure all browser installations are updated promptly, particularly in environments where users may encounter untrusted PDF content. Additional protective measures include implementing browser security policies that restrict PDF handling, using sandboxing technologies, and deploying web application firewalls that can detect and block malicious PDF content. Security teams should also consider monitoring for unusual browser behavior or memory access patterns that might indicate exploitation attempts. The vulnerability underscores the importance of regular security updates and the critical nature of memory safety in browser implementations, as modern browsers handle increasingly complex web content that demands robust memory management systems to prevent exploitation of such fundamental flaws.