CVE-2026-121055 in Chrome
Summary
by MITRE • 11/03/2026
Incomplete cleanup in DevTools in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to bypass system access restrictions via a crafted Chrome extension. (Chromium security severity: Low)
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified as an incomplete cleanup issue within the Developer Tools component of Google Chrome, specifically affecting versions prior to 157.0.8103.38, represents a subtle but significant flaw in how browser extensions interact with system-level access controls. This security severity is classified as Low by Chromium standards, yet it carries substantial implications for user privacy and application integrity when exploited through maliciously crafted Chrome extensions. The core of the issue lies in the lifecycle management of resources associated with extension contexts within the DevTools environment. When an extension utilizes Developer Tools to inspect or manipulate web content, it often requires elevated privileges or specific permissions that are normally sandboxed from general browsing activities. In this instance, the cleanup process responsible for revoking these extended permissions and releasing associated memory handles was not executed completely upon the termination of a session or the removal of the extension context.
From a technical perspective, this flaw allows a remote attacker who has successfully installed a malicious Chrome extension to maintain persistent access to system resources that should have been restricted once the interaction with Developer Tools concluded. The incomplete cleanup means that state variables, event listeners, or permission grants remain active in memory even after they are no longer needed by the legitimate user workflow. This residual state can be leveraged by an attacker to bypass intended security boundaries. For example, if an extension had temporarily granted access to sensitive DOM elements or internal browser APIs during a debugging session, the failure to fully revoke these rights allows subsequent operations within that same context to proceed without proper authorization checks. The attacker crafts the extension to exploit this window of opportunity, ensuring that even after the user believes they have closed the developer tools or navigated away from the inspected page, the underlying permissions remain valid and accessible for further exploitation.
The operational impact of this vulnerability centers on unauthorized access to restricted system functions and potential data exfiltration. By bypassing these access restrictions, an attacker can potentially read sensitive information stored in browser memory, intercept network requests that were previously secured by extension boundaries, or manipulate the state of web applications in ways that violate user expectations. While the severity is rated as low due to the requirement for a malicious extension installation, which typically involves social engineering or supply chain compromise, the ability to bypass access controls remains a critical concern for enterprise environments and high-security users who rely on strict isolation between browser components. The attack vector requires initial code execution via the extension platform, but once established, it provides a foothold that persists beyond normal session lifecycles, complicating forensic analysis and remediation efforts by leaving traces of unauthorized activity in active memory spaces.
Mitigation strategies primarily involve updating to Google Chrome version 157.0.8103.38 or later, where the cleanup logic has been corrected to ensure all permissions are properly revoked and resources released upon context termination. Administrators should enforce strict policies regarding extension installation, utilizing whitelisting mechanisms in enterprise environments to prevent unauthorized extensions from being deployed on user devices. Additionally, users should exercise caution when installing extensions that request access to Developer Tools or require broad permissions, as these can serve as vectors for such exploitation. Regular auditing of installed extensions and monitoring for unusual memory usage patterns by browser processes can also aid in detecting potential abuse of this vulnerability before significant damage occurs. The fix aligns with general best practices for secure software lifecycle management, emphasizing the importance of rigorous resource cleanup to prevent state leakage that could lead to privilege escalation or data breaches.
This incident highlights the complexity of modern web browsers where multiple subsystems like DevTools must interact seamlessly while maintaining strict security boundaries. It underscores the necessity for developers and browser vendors to implement robust finalization routines that account for all possible exit paths, including unexpected terminations or context switches. By addressing this incomplete cleanup issue, Google Chrome reinforces its commitment to preventing unauthorized access through extension-based attack vectors. The integration of such fixes into regular release cycles ensures that users are protected against evolving threats that exploit subtle implementation flaws in browser internals. Continued vigilance and adherence to security updates remain the most effective defense against these types of vulnerabilities, which rely on precise timing and state manipulation to achieve their objectives.