CVE-2026-91748 in Chrome
Summary
by MITRE • 09/15/2026
Race condition in Extensions in Google Chrome on on Mac prior to 153.0.8010.47 allowed a remote attacker who had compromised the renderer process and leveraged social engineering to potentially execute arbitrary code outside the sandbox via UI Interaction. (Chromium security severity: High)
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified in Google Chrome prior to version 153.0.8010.47 represents a critical race condition within the Extensions subsystem on macOS, classified with high severity by Chromium security teams. This flaw stems from improper synchronization mechanisms when handling state transitions or resource access during extension operations. Specifically, the issue arises when multiple threads or processes attempt to interact with shared data structures associated with browser extensions without adequate locking or atomicity guarantees. In a typical race condition scenario, an attacker can exploit the timing window between a check for permissions and the subsequent use of those permissions, allowing them to bypass intended security controls. This specific instance involves the extension system's handling of user interface interactions, where the state of the application is not consistently validated before executing actions that affect the broader browser environment or external processes.
The operational impact of this vulnerability is significant because it allows for sandbox escape under specific conditions. An attacker who has already compromised a renderer process through other means, such as exploiting a separate memory corruption bug in web content rendering, can leverage social engineering techniques to manipulate user behavior. By tricking the user into interacting with a malicious extension or interface element crafted by the attacker, they can trigger the race condition. The exploitation path relies on precise timing and user interaction to gain control over execution flow outside the restrictive Chrome sandbox environment. Once this boundary is crossed, the attacker gains the ability to execute arbitrary code with higher privileges than those granted to standard web content, potentially leading full system compromise depending on the context in which the browser operates.
From a classification perspective, this vulnerability aligns closely with CWE-362, Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). The core failure is the lack of proper synchronization when accessing shared resources within the extension framework. Furthermore, the exploitation technique maps to MITRE ATT&CK techniques related to privilege escalation and defense evasion. Specifically, it relates to T1055, Process Injection or T1218, Signed Binary Proxy Execution, if the attacker leverages legitimate system binaries after escaping the sandbox. The use of social engineering highlights the importance of human factors in security, aligning with ATT&CK tactic TA0001, Initial Access, where trust is abused to facilitate further exploitation.
Mitigation strategies for this vulnerability primarily involve updating Google Chrome to version 153.0.8010.47 or later, which includes the necessary code fixes to enforce proper synchronization and state validation within the extension system. Organizations should ensure that automatic updates are enabled to receive security patches promptly. Additionally, administrators can implement policies to restrict the installation of third-party extensions from untrusted sources, thereby reducing the attack surface available to potential adversaries. Users should be educated on recognizing social engineering attempts and verifying the legitimacy of prompts requesting permissions or interactions with browser interfaces. Regular auditing of installed extensions and removal of unused add-ons further reduces the risk profile associated with this class of vulnerabilities.