CVE-2026-121218 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 execute arbitrary code inside the sandbox via a crafted HTML page. (Chromium security severity: Medium)
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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 browser's sandboxing mechanisms. Type confusions occur when an application incorrectly interprets the data type of a value in memory, leading to operations being performed on data structures as if they were a different type. In the context of V8, this typically involves the misinterpretation of JavaScript objects or their internal representations during Just-In-Time compilation or garbage collection processes. When such a confusion is triggered by a crafted HTML page served from a remote server, it allows an attacker to manipulate memory layout in ways that bypass standard security checks, effectively creating a pathway for arbitrary code execution within the browser's restricted sandbox environment.
From a technical perspective, this flaw exploits inconsistencies between how V8 tracks object types and how those objects are accessed or modified during runtime. The engine relies on hidden classes and type feedback to optimize performance, but if an attacker can craft input that forces the engine to assume one data structure while another is present in memory, it becomes possible to read or write arbitrary memory locations. This discrepancy enables the construction of primitive read-write capabilities, which are essential for escalating privileges from a low-privilege sandboxed context to full code execution on the host system. The severity is classified as medium by Chromium security standards because, while exploitation requires specific conditions and crafted input, the impact involves breaking out of the browser's isolation boundaries, potentially leading to remote code execution without user interaction beyond visiting the malicious webpage.
The operational impact of this vulnerability extends beyond simple script injection or cross-site scripting attacks. By achieving arbitrary code execution inside the sandbox, an attacker can bypass security features such as site-isolation and process separation that are designed to limit the damage caused by web-based exploits. This capability allows for potential data exfiltration, installation of persistent malware, or further lateral movement within a network if the compromised browser is used in conjunction with other vulnerabilities or social engineering tactics. The existence of this flaw highlights the ongoing challenges in maintaining memory safety in complex engines like V8, where performance optimizations often introduce subtle bugs that can be leveraged by sophisticated threat actors to compromise user systems remotely.
Mitigation strategies primarily involve updating Google Chrome and its underlying Chromium components to version 157.0.8103.38 or later, which includes patches for the identified type confusion logic in V8. Users should ensure automatic updates are enabled to receive security fixes promptly as they become available. For organizations managing large fleets of devices, deploying enterprise update policies that enforce timely patching is critical to reducing exposure windows. Additionally, employing browser hardening techniques such as disabling JavaScript execution on untrusted sites or using extensions that restrict script behavior can provide an additional layer of defense against exploitation attempts targeting this specific vulnerability class.
This incident aligns with Common Weakness Enumeration (CWE) category CWE-843, which covers access to incorrect type during interpretation, and is relevant to MITRE ATT&CK technique T1059, specifically Command and Scripting Interpreter subcategories where attackers leverage system interpreters for execution. The exploitation vector corresponds to remote code execution via a web-based attack pattern, emphasizing the importance of keeping browser engines updated to address memory safety issues that persist despite rigorous testing processes in modern software development lifecycles.