CVE-2016-1646 in Chrome
Summary
by MITRE
The Array.prototype.concat implementation in builtins.cc in Google V8, as used in Google Chrome before 49.0.2623.108, does not properly consider element data types, which allows remote attackers to cause a denial of service (out-of-bounds read) or possibly have unspecified other impact via crafted JavaScript code.
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Analysis
by VulDB Data Team • 04/23/2026
The vulnerability described in CVE-2016-1646 represents a critical flaw in Google V8's JavaScript engine implementation that affects Google Chrome versions prior to 49.0.2623.108. This issue stems from improper handling of element data types within the Array.prototype.concat method, which is a fundamental operation in JavaScript programming. The vulnerability resides in the builtins.cc file of the V8 engine, specifically in how it processes array concatenation operations, creating a potential pathway for malicious JavaScript code to exploit the underlying memory management mechanisms.
The technical flaw manifests when the V8 engine fails to properly validate or consider the data types of elements during array concatenation operations. This improper type handling creates conditions where an attacker can craft specific JavaScript code that triggers an out-of-bounds read condition, allowing for memory access beyond the intended array boundaries. The vulnerability can potentially be leveraged for more severe impacts beyond simple denial of service, including arbitrary code execution or information disclosure, depending on the specific attack scenario and system configuration. This type of vulnerability falls under CWE-129, which addresses improper validation of array indices, and represents a classic example of buffer over-read conditions that can be exploited in web browser environments.
The operational impact of this vulnerability is significant for users of affected Chrome versions, as it can be exploited through malicious web pages without requiring any user interaction beyond visiting the compromised site. Remote attackers can craft JavaScript payloads that, when executed in the browser context, trigger the flawed concat implementation and potentially gain unauthorized access to system resources or execute malicious code. The vulnerability affects the core JavaScript engine functionality, meaning that any web application or website that utilizes array concatenation operations could become a vector for exploitation. This makes it particularly dangerous in environments where users might encounter untrusted web content, as the attack surface extends to any JavaScript code that might be executed within the browser.
Mitigation strategies for CVE-2016-1646 primarily focus on updating to patched versions of Google Chrome, specifically version 49.0.2623.108 or later, which contain the necessary fixes to properly handle element data types during array concatenation operations. Organizations should also implement additional security measures such as content security policies, sandboxing mechanisms, and regular security updates to reduce the risk of exploitation. Browser vendors and security teams should consider implementing automatic update mechanisms and monitoring for similar vulnerabilities in other JavaScript engine implementations. The fix typically involves strengthening the type validation logic within the concat method implementation to ensure proper bounds checking and element type handling, preventing the out-of-bounds memory access conditions that enable exploitation. This vulnerability highlights the importance of rigorous input validation and proper memory management in JavaScript engines, particularly in environments where untrusted code execution is possible.