CVE-2026-121221 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 • 11/03/2026
The vulnerability identified as a type confusion issue within the V8 JavaScript engine, which powers Google Chrome prior to version 157.0.8103.38, represents a critical failure in memory safety and runtime type checking mechanisms. Type confusions occur when an application incorrectly interprets the data type of a variable or object during execution, leading to operations being performed on data structures that do not match their expected format. In the context of V8, this flaw allows for the manipulation of internal heap objects where the engine fails to properly validate the consistency between JavaScript-level types and C++-level representations. This discrepancy creates an opportunity for a remote attacker to craft a malicious HTML page containing specific JavaScript code designed to trigger this misinterpretation. By exploiting the mismatch in type handling, the attacker can cause V8 to perform invalid memory accesses or execute instructions based on corrupted state information within the engine's runtime environment.
The operational impact of this vulnerability is severe due to its potential for arbitrary code execution within Chrome’s sandboxed process model. While modern browsers employ multiple layers of defense such as site isolation and hardware-enforced stack protection, a successful exploitation of a type confusion in V8 can bypass these controls by achieving out-of-bounds reads or writes that allow the attacker to gain control over critical program flow indicators like return addresses or function pointers. The Chromium security team has classified this issue with a High severity rating, reflecting its potential to lead to full compromise of the user's system if combined with other techniques for sandbox escape. An attacker hosting a malicious webpage could lure a victim into visiting it, thereby initiating the exploit chain without any further interaction required from the user beyond loading the page in an affected version of Chrome.
From a classification perspective, this vulnerability aligns closely with CWE-843, which describes access to incorrect type assumption errors, and specifically relates to improper handling of dynamic types within complex software systems like JavaScript engines. Furthermore, the exploitation technique falls under MITRE ATT&CK tactics related to initial access via drive-by compromise and execution through browser-based attacks. The ability to execute arbitrary code inside the sandbox highlights the importance of robust input validation and strict type enforcement in low-level components that handle high-level scripting languages. Such vulnerabilities are particularly dangerous because they often require sophisticated payload construction but can result in significant privilege escalation if the sandbox boundaries are breached.
Mitigation strategies primarily involve updating Google Chrome to version 157.0.8103.38 or later, where these type checking mechanisms have been hardened and patched by the V8 development team. For organizations managing large fleets of endpoints, ensuring automatic update policies are enforced is crucial to prevent exposure to such remote code execution risks. Additionally, security teams should monitor for indicators of compromise associated with drive-by download campaigns that target browser vulnerabilities. While user education regarding suspicious links remains relevant, technical controls like endpoint detection and response systems configured to detect anomalous behavior in browser processes can provide an additional layer of defense against exploitation attempts targeting this specific class of memory safety flaws.