CVE-2026-121057 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: 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 assumes that a variable or object is of one data type while it actually contains another, leading to undefined behavior during execution. In the context of V8, this flaw likely involved improper handling of JavaScript objects where internal representations were not correctly validated against their declared types before memory access operations took place. This specific class of vulnerability allows for arbitrary read and write primitives within the browser's sandboxed environment, which is a significant escalation from typical cross-site scripting or content injection attacks because it bypasses standard web security boundaries by exploiting low-level engine logic rather than high-level application code.
From an operational perspective, this flaw enabled remote attackers to execute arbitrary code inside the Chrome sandbox through a crafted HTML page. The attack vector relies on social engineering or drive-by download tactics where a victim is directed to visit a maliciously constructed webpage containing specially formatted JavaScript that triggers the type confusion bug. Once triggered, the attacker gains control over memory operations, allowing them to manipulate object structures and heap layouts. This capability facilitates further exploitation steps such as sandbox escape techniques, which would allow code execution outside the restricted browser context with higher privileges. The Chromium security team classified this issue as High severity due to its potential for remote code execution without user interaction beyond visiting a webpage, highlighting the critical nature of maintaining strict type integrity within high-performance JavaScript engines used by billions of users worldwide.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) categories such as CWE-843: Access of Incorrect Type and CWE-120: Buffer Copy without Checking Size of Input, although in this case the buffer aspect is more about logical type misinterpretation than simple overflow. It also maps to MITRE ATT&CK techniques related to initial access via drive-by compromise and potentially privilege escalation if sandbox escape was successfully achieved through subsequent exploitation stages leveraging the memory corruption primitive provided by the type confusion. The existence of such flaws underscores the complexity inherent in managing dynamic typing systems like JavaScript while ensuring they map correctly onto statically typed underlying C++ implementations within V8.
Mitigation strategies primarily involve applying the vendor-supplied patch included in Google Chrome version 157.0.8103.38 and later releases, which corrects the type checking logic to prevent misinterpretation of object types during runtime execution. Organizations should ensure that all endpoints running affected versions are updated immediately to close this attack surface. Additionally, users can employ browser hardening techniques such as disabling JavaScript for untrusted sites or using extensions that restrict script execution on suspicious domains. Continuous monitoring and automated vulnerability management systems should be utilized to detect exposure to known type confusion vulnerabilities in widely deployed software components like V8, ensuring rapid remediation before exploitation becomes widespread in the wild.