CVE-2026-121158 in Chrome
Summary
by MITRE • 11/03/2026
Information leak in Paint in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to obtain sensitive information 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 paint component of Google Chrome, specifically affecting versions prior to 157.0.8103.38, represents a significant breach in browser isolation and data confidentiality mechanisms. This flaw allows a remote attacker to extract sensitive information from web pages or internal browser states by leveraging a crafted HTML page. The severity is classified as Medium within the Chromium security framework, indicating that while the exploit requires user interaction such as visiting a malicious site, the potential for unauthorized data access poses a tangible risk to user privacy and application integrity.
At its core, this vulnerability stems from improper handling of graphical rendering operations during the paint phase of the browser's lifecycle. The Chrome engine processes HTML content by converting it into visual elements through various subsystems including layout, style computation, and painting. In affected versions, certain edge cases in how these painted resources are managed or exposed to JavaScript contexts allowed for unintended data leakage. When a user navigates to a specially crafted webpage containing malicious scripts, the browser's rendering engine inadvertently exposes memory contents or internal state variables that should remain isolated from web content. This typically occurs when graphical buffers or canvas elements retain references to sensitive data without proper clearing or isolation checks before being accessible via standard web APIs.
The operational impact of this vulnerability centers on unauthorized information disclosure. An attacker can construct a malicious webpage designed to trigger the specific rendering conditions required to exploit the flaw. Once executed, the crafted script can read out values that were not intended for public access, such as session tokens, authentication cookies, or other sensitive data stored in browser memory. This type of attack falls under the category of cross-site scripting variants where the vector is not code injection per se but rather side-channel information leakage through improper resource management. The ability to obtain this data enables further attacks including account takeover, session hijacking, and deeper reconnaissance against targeted users or organizations relying on Chrome for secure browsing activities.
From a classification perspective, this vulnerability aligns with CWE-200 which defines an Information Exposure where security-sensitive information is disclosed without explicit intent. It also relates to ATT&CK technique T1537 which involves Transfer Data to Cloud Account via Exfiltration Over Alternative Protocol although in this context the exfiltration occurs locally through browser APIs rather than network protocols. The root cause often traces back to CWE-400 concerning Uncontrolled Resource Consumption or improper memory management practices within the rendering pipeline that fail to sanitize outputs before exposing them to less trusted contexts like JavaScript execution environments.
Mitigation strategies primarily involve updating Google Chrome to version 157.0.8103.38 or later where these painting logic errors have been corrected by Chromium developers. Administrators should enforce automatic update policies across all endpoints using the browser to ensure timely patch deployment. For organizations unable to immediately upgrade, network-level controls such as Content Security Policy headers can help restrict script execution from untrusted sources reducing the likelihood of exploitation although they do not fix the underlying engine flaw. Additionally monitoring for unusual patterns in memory usage or unexpected data access by web pages may provide early detection indicators until patches are applied. Regular security audits and penetration testing focusing on browser-based attacks remain essential components of a comprehensive defense-in-depth strategy against such vulnerabilities.