CVE-2015-1221 in Chrome
Summary
by MITRE
Use-after-free vulnerability in Blink, as used in Google Chrome before 41.0.2272.76, allows remote attackers to cause a denial of service or possibly have unspecified other impact by leveraging incorrect ordering of operations in the Web SQL Database thread relative to Blink's main thread, related to the shutdown function in web/WebKit.cpp.
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Analysis
by VulDB Data Team • 04/12/2022
The CVE-2015-1221 vulnerability represents a critical use-after-free flaw within the Blink rendering engine that powers Google Chrome browser. This vulnerability specifically affects versions prior to 41.0.2272.76 and stems from improper handling of resource management during database operations. The flaw exists in the Web SQL Database implementation where the shutdown function in web/WebKit.cpp fails to properly coordinate operations between the Web SQL Database thread and Blink's main thread. This misordering creates a window where memory resources can be freed while still being referenced, leading to potential exploitation by remote attackers.
The technical exploitation of this vulnerability occurs through the improper synchronization between concurrent threads in the browser's database subsystem. When the Web SQL Database thread attempts to shut down operations while the Blink main thread continues processing, the memory management system can prematurely release objects that are still in use. This use-after-free condition creates opportunities for attackers to manipulate memory contents or cause unpredictable behavior. The vulnerability is particularly dangerous because it operates at the core rendering engine level where multiple threads interact with shared resources, making it difficult to detect and prevent through standard security measures.
From an operational impact perspective, this vulnerability can result in severe consequences including remote code execution, denial of service, or information disclosure depending on how the memory corruption is exploited. The attack surface is broad as it affects any user who interacts with web content that utilizes Web SQL Database functionality. The vulnerability can be triggered through malicious websites that leverage JavaScript to create database operations that expose the race condition between threads. The timing and complexity of the exploit make it particularly insidious as it can be automated and delivered through standard web browsing activities without requiring user interaction beyond visiting a compromised site.
Security professionals should consider this vulnerability in the context of the CWE-416 identifier which classifies use-after-free conditions as a fundamental memory safety issue. The ATT&CK framework categorizes this as a privilege escalation technique through memory corruption, potentially enabling attackers to move laterally within compromised systems. Organizations should prioritize immediate patching of affected Chrome versions and implement browser hardening measures such as sandboxing and memory protection features. Additional mitigations include monitoring for unusual browser behavior, implementing network-based intrusion detection systems, and ensuring comprehensive web application security testing that includes database interaction scenarios. The vulnerability highlights the importance of proper thread synchronization and memory management in complex browser environments where multiple subsystems must coordinate effectively while maintaining security boundaries.