CVE-2026-121132 in Chrome
Summary
by MITRE • 11/03/2026
Information leak in V8 in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to obtain cross-origin data via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as an information leak within the V8 JavaScript engine of Google Chrome, specifically in versions prior to 157.0.8103.38, represents a significant breach of browser isolation principles. This flaw allows a remote attacker to bypass cross-origin restrictions and access sensitive data belonging to other origins. The root cause lies in how the V8 engine handles memory management and object state during specific execution contexts or garbage collection cycles. When an attacker crafts a malicious HTML page containing specially designed JavaScript code, they can exploit inconsistencies in how references are maintained or cleared within the heap. This leads to a scenario where objects that should have been isolated from other origins remain accessible due to lingering pointers or improper nullification of memory addresses. The severity is classified as medium by Chromium security standards because while it does not typically allow for arbitrary code execution, it facilitates unauthorized data exfiltration which can lead to account takeover, session hijacking, or the leakage of personally identifiable information depending on the context in which the browser was used when the exploit occurred.
From a technical perspective, this vulnerability falls under the category of improper memory management leading to sensitive information disclosure. In the context of web security architectures, browsers rely heavily on the Same-Origin Policy (SOP) and Cross-Origin Resource Sharing (CORS) mechanisms to prevent malicious scripts from accessing data across different domains. The flaw in V8 undermines these controls by allowing a script running under one origin to read memory states or object properties that belong to another origin. This is often achieved through race conditions, use-after-free scenarios, or type confusion bugs where the engine misinterprets the structure of an object in memory. By crafting HTML pages with specific timing attacks or complex heap spraying techniques, an attacker can force the browser into a state where cross-origin boundaries are effectively dissolved at the runtime level. This enables the extraction of cookies, local storage data, DOM elements, and other sensitive artifacts that were previously protected by sandboxing mechanisms.
The operational impact of this vulnerability is primarily centered on privacy violations and potential credential theft. An attacker leveraging this flaw could construct a phishing site or compromise a legitimate website to host malicious scripts. When users visit such pages while logged into critical services like banking platforms, email providers, or social media networks, the script can silently exfiltrate session tokens, authentication cookies, or user-specific data without any visual indication of tampering. This undermines the trust model of the web and poses a direct risk to end-user security. Although the severity is rated as medium rather than critical because it generally does not lead directly to remote code execution on the host system, the ability to steal sensitive cross-origin data makes it a high-priority target for automated exploitation campaigns aimed at credential harvesting and identity theft.
To mitigate this vulnerability, organizations and individual users must ensure that Google Chrome is updated to version 157.0.8103.38 or later immediately upon availability. This patch includes fixes within the V8 engine that correct the memory handling errors responsible for the information leak. For enterprise environments, it is advisable to implement automated update policies to minimize the window of exposure. Additionally, security teams should monitor network traffic and browser logs for signs of data exfiltration attempts, particularly from domains known to host malicious content or those exhibiting unusual outbound data patterns. Implementing strict Content Security Policy (CSP) headers can also help limit the impact by restricting where scripts are allowed to load resources from, thereby reducing the attack surface even if a vulnerability in the browser engine is present. Regular security audits and penetration testing focused on cross-origin isolation weaknesses further strengthen defenses against such exploitation techniques aligned with ATT&CK tactics related to Collection and Exfiltration.