CVE-2026-121068 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 • 11/04/2026
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 failure in memory safety and runtime type checking mechanisms. Type confusion vulnerabilities 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 typically involves the engine misinterpreting the structure or properties of JavaScript objects due to improper handling of polymorphic inline caches or incorrect assumptions about hidden classes used for optimization. When an attacker crafts a specific HTML page containing malicious JavaScript code, they can exploit these inconsistencies in type inference to manipulate how memory is accessed and interpreted by the browser's sandboxed environment.
The operational impact of this vulnerability is severe because it allows for arbitrary code execution within the context of the renderer process. Although Chrome employs multiple layers of defense such as site isolation and sandboxing to limit the blast radius of a compromise, successfully exploiting a type confusion bug can bypass these protections by achieving memory corruption that leads to control flow hijacking. An attacker could potentially execute shellcode or other malicious payloads on the victim's machine, leading to full system compromise if further exploitation steps are taken to escape the browser sandbox entirely. This aligns with common attack patterns where initial access is gained through a crafted web page, leveraging social engineering or drive-by download tactics to trigger the vulnerable code path without user interaction beyond visiting the site.
From a classification perspective, this vulnerability maps directly to CWE-843, which describes Accessing Memory with Incorrect Type Specification, and often involves elements of CWE-120, Buffer Overflow without Check for Size Before Writing to Buffer, depending on how the type confusion leads to out-of-bounds writes or reads. In terms of offensive security frameworks like MITRE ATT&CK, this exploit technique falls under Tactic 6: Defense Evasion, specifically techniques related to bypassing application sandbox restrictions and potentially Tactic 7: Discovery if used for reconnaissance within the compromised environment. The high severity rating assigned by Chromium reflects the ease with which such bugs can be chained into full remote code execution exploits in modern browsers that rely heavily on JIT compilation features of V8.
Mitigation strategies primarily involve updating to Google Chrome version 157.0.8103.38 or later, where the underlying type checking logic and bounds verification mechanisms have been patched by the Chromium security team. For organizations unable to update immediately, network-level controls such as web application firewalls can be configured to detect and block requests containing suspicious JavaScript patterns known to trigger V8 vulnerabilities, although this is less effective against zero-day exploits. Additionally, enabling strict Content Security Policy headers helps mitigate the impact of successful exploitation by restricting script execution sources and preventing inline scripts from running unless explicitly allowed. Regular patch management cycles are essential to address these high-severity issues promptly given their potential for widespread automated exploitation in the wild.