CVE-2026-121054 in Chrome
Summary
by MITRE • 11/03/2026
Improper state validation in XML in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to bypass web origin policy via a crafted HTML page. (Chromium security severity: Low)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as an improper state validation issue within the Extensible Markup Language processing components of Google Chrome prior to version 157.0.8103.38 represents a significant deviation from expected browser security boundaries. This flaw specifically impacts how the rendering engine handles XML documents, particularly when such content is embedded or referenced via HTML pages. The core technical deficiency lies in the failure to properly validate the state of an object during parsing operations, which allows for inconsistent behavior between different stages of document processing. When a malicious actor crafts an HTML page that leverages specific XML structures, they can exploit this inconsistency to manipulate how the browser interprets the origin and scope of resources loaded within that context. This misalignment in state management creates a pathway for unauthorized access patterns that would otherwise be blocked by standard security controls.
From a technical perspective, web origin policies are fundamental mechanisms designed to isolate content from different sources to prevent malicious scripts on one page from obtaining access to sensitive data on another page with a different origin. The vulnerability exploits the gap between how XML is parsed and how its resulting objects are subjected to same-origin policy checks. By crafting an HTML page that triggers specific edge cases in the XML parser, an attacker can cause the browser to treat content as originating from a trusted domain when it actually originates from an untrusted or malicious source. This bypass allows for potential data exfiltration, session hijacking, or unauthorized interaction with web applications hosted on legitimate domains. The severity is classified as low by Chromium standards because successful exploitation typically requires user interaction and specific environmental conditions, yet the implications remain serious due to the fundamental nature of origin isolation in modern web security architectures.
The operational impact of this vulnerability centers on the potential for cross-origin data leakage or unauthorized actions performed under the guise of a trusted site. An attacker could construct a phishing page that loads malicious XML content designed to exploit this state validation flaw. If successful, the browser may allow scripts within that context to access cookies, local storage, or other sensitive information belonging to users logged into legitimate services on different domains. This undermines the trust model upon which web applications rely, potentially leading to account takeover scenarios where an attacker gains persistent access by stealing session tokens through this indirect vector. While direct remote code execution is not implied, the ability to bypass origin policies facilitates a wide range of secondary attacks including credential theft and unauthorized API calls that compromise user privacy and data integrity.
Mitigation strategies primarily involve updating Google Chrome to version 157.0.8103.38 or later, where these state validation checks have been corrected to ensure consistent enforcement of origin policies across all XML parsing contexts. For organizations unable to immediately patch client systems, implementing strict Content Security Policy headers can help mitigate the risk by restricting how resources are loaded and executed within web pages. Additionally, developers should avoid embedding untrusted XML content directly into HTML documents without rigorous sanitization or using iframe sandboxing attributes to limit the capabilities of embedded content. Monitoring for unusual cross-origin requests originating from local file protocols or unexpected domains can also aid in detecting potential exploitation attempts in real-time environments.
This vulnerability aligns with Common Weakness Enumeration category CWE-20, which describes improper input validation, specifically regarding how state is managed during parsing operations that affect security boundaries. It also relates to ATT&CK technique T1534, known as Internal Spearphishing, where attackers use social engineering combined with technical exploits like this one to gain initial access or escalate privileges within a target environment by tricking users into visiting malicious pages that exploit browser inconsistencies. Understanding these mappings helps in categorizing the threat landscape and prioritizing remediation efforts based on established industry standards for vulnerability management and security posture improvement.