CVE-2026-121226 in Chrome
Summary
by MITRE • 11/03/2026
Type confusion in V8 in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to potentially execute arbitrary code inside the sandbox via a crafted HTML page. (Chromium security severity: High)
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified as a type confusion flaw within the V8 JavaScript engine, which powers Google Chrome prior to version 157.0.8103.38, represents a critical memory safety issue that undermines the integrity of the browser's execution environment. Type confusions occur when an application incorrectly interprets the data type of a variable or object in memory, leading to operations being performed on data structures with incompatible types. In the context of V8, this typically involves the misinterpretation of JavaScript objects during Just-In-Time compilation or garbage collection processes. When such a flaw is present, it allows for arbitrary read and write access to adjacent memory regions, which can be leveraged by an attacker to bypass security mechanisms like sandboxing and execute code with elevated privileges within the browser process.
From a technical perspective, this vulnerability stems from improper handling of object types during runtime operations. The V8 engine relies on hidden classes or type tags to track the structure and properties of JavaScript objects for optimization purposes. If these internal representations are not correctly synchronized with actual memory layouts due to a logic error in the compiler or interpreter, an attacker can craft specific HTML pages containing malicious JavaScript that triggers this mismatch. By carefully constructing object states and triggering specific execution paths, the attacker forces V8 to treat one type of data as another, such as interpreting a pointer as an integer or vice versa. This misinterpretation facilitates out-of-bounds memory accesses or arbitrary code execution primitives, which are foundational steps in developing exploit chains that escape the browser sandbox.
The operational impact of this vulnerability is severe due to its potential for remote code execution via a crafted HTML page. An attacker does not need physical access or user interaction beyond visiting a malicious website hosted on a server under their control. Once a victim loads the specially constructed webpage, the embedded script exploits the type confusion in V8 to gain arbitrary code execution capabilities within the browser's process space. Although modern browsers employ sandboxing techniques that restrict what executed code can do, such as limiting file system access or network permissions, escaping this sandbox is often possible through additional exploitation steps following a successful memory corruption primitive like type confusion. This could lead to full compromise of the user's machine if combined with other vulnerabilities or misconfigurations, resulting in data theft, installation of malware, or use of the device for further attacks.
This flaw aligns closely with Common Weakness Enumeration (CWE) category CWE-843, which describes access to incorrect type interpretation, and is often a precursor to more severe issues like CWE-120 Buffer Overflow if it leads to memory corruption that overwrites control flow data. In terms of the MITRE ATT&CK framework, this vulnerability facilitates techniques associated with Initial Access via Spearphishing Link or Drive-by Compromise, specifically leveraging browser vulnerabilities for code execution. It also relates to Defense Evasion through Sandbox Escape and Privilege Escalation if the attacker successfully breaks out of the restricted environment. The severity is classified as High by Chromium security standards because it provides a reliable path from remote web content to arbitrary code execution without requiring user interaction beyond visiting the page, making it a prime target for automated exploitation campaigns on the dark web or in targeted attacks.
Mitigation strategies primarily involve updating Google Chrome and its underlying V8 engine to version 157.0.8103.38 or later, where these type confusion issues have been patched by correcting the internal logic that handles object types during compilation and execution. For organizations managing large fleets of devices, ensuring automatic update policies are enforced is critical to prevent exposure to such remote exploits. Additionally, deploying browser hardening techniques can reduce the attack surface. These include disabling JavaScript in untrusted sites where possible, using extensions that block script execution on specific domains, or employing enterprise-grade security solutions that monitor for anomalous behavior indicative of exploit attempts. While these measures do not fix the underlying vulnerability, they significantly raise the barrier for attackers attempting to leverage this flaw effectively. Regular patching remains the most effective defense against zero-day and known vulnerabilities in widely used software components like V8.