CVE-2015-6765 in Chrome
Summary
by MITRE
Use-after-free vulnerability in content/browser/appcache/appcache_update_job.cc in Google Chrome before 47.0.2526.73 allows remote attackers to execute arbitrary code or cause a denial of service by leveraging the mishandling of AppCache update jobs.
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Analysis
by VulDB Data Team • 06/28/2022
The vulnerability identified as CVE-2015-6765 represents a critical use-after-free flaw within Google Chrome's application cache management system. This security weakness exists in the appcache_update_job.cc file and affects Chrome versions prior to 47.0.2526.73, making it a significant concern for users running outdated browser versions. The vulnerability stems from improper handling of AppCache update jobs, which are responsible for managing web application caching mechanisms that allow websites to function offline and improve performance by storing resources locally. The use-after-free condition occurs when memory that has been freed is still referenced, creating opportunities for malicious code execution or system instability.
The technical exploitation of this vulnerability leverages the improper memory management within Chrome's application cache subsystem where an attacker can manipulate the AppCache update process to trigger a use-after-free scenario. When Chrome processes application cache updates, it allocates memory for cache job objects and subsequently frees this memory upon completion. However, under specific conditions involving malicious web content, the system fails to properly invalidate references to freed memory blocks, allowing attackers to manipulate the freed memory through carefully crafted payloads. This memory corruption can lead to arbitrary code execution with the privileges of the Chrome process, potentially enabling attackers to bypass security boundaries and escalate their access within the user's browsing environment. The flaw aligns with CWE-416, which specifically addresses use-after-free vulnerabilities where memory is accessed after it has been freed, and represents a classic example of memory safety issues that have plagued web browsers for years.
From an operational perspective, this vulnerability presents a severe threat to user security as it allows remote code execution without requiring user interaction beyond visiting a malicious website. Attackers can craft web pages that trigger the AppCache update process in a manner that causes the use-after-free condition, potentially leading to complete system compromise when combined with other attack vectors or when the browser is running with elevated privileges. The impact extends beyond simple denial of service scenarios, as successful exploitation could result in persistent backdoors, data theft, or complete system takeover depending on the execution environment. This vulnerability demonstrates the critical importance of maintaining up-to-date browser software, as the window of exploitation exists for users running vulnerable Chrome versions, and represents a significant risk in enterprise environments where browser security is paramount. The attack surface is particularly concerning given that application cache functionality is widely used across modern web applications, making this vulnerability potentially exploitable across a broad range of legitimate websites.
The recommended mitigation strategy centers on immediate patch deployment for Chrome versions prior to 47.0.2526.73, as this represents the most effective defense against exploitation of the use-after-free condition. Organizations should implement comprehensive patch management protocols to ensure all Chrome installations are updated to the latest secure versions, particularly given the remote execution capability of this vulnerability. Additional protective measures include implementing browser hardening techniques such as sandboxing, privilege separation, and content security policies that limit the impact of potential exploitation. Network-level defenses such as web application firewalls and intrusion detection systems can help detect and block malicious web content attempting to exploit this vulnerability, though the most reliable protection remains timely software updates. Security professionals should also monitor for indicators of compromise related to this vulnerability, including unusual browser behavior or memory corruption patterns that might suggest exploitation attempts. The vulnerability serves as a reminder of the critical need for continuous security assessment and the importance of addressing memory safety issues in complex software systems like web browsers that handle untrusted content from diverse sources.