CVE-2026-121211 in Chrome
Summary
by MITRE • 11/03/2026
Use after free in PowerBookmarks in Google Chrome prior to 157.0.8103.38 allowed a remote attacker who had compromised the renderer process and leveraged social engineering to execute arbitrary code outside the sandbox via a crafted Chrome extension. (Chromium security severity: High)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in Google Chrome prior to version 157.0.8103.38 represents a critical memory corruption flaw within the PowerBookmarks component, classified technically as an out-of-bounds use or use-after-free error. This specific type of vulnerability arises when software continues to use a pointer after it has been freed from memory, potentially leading to unpredictable behavior including crashes, data corruption, and most critically in this context, arbitrary code execution. The root cause lies in the improper management of memory lifecycle within the extension handling subsystem, where references to deallocated objects were retained and accessed by subsequent operations without adequate validation or nullification checks.
From a security architecture perspective, this flaw is particularly dangerous because it bridges the gap between the renderer process sandbox and the browser's privileged main process. Chrome employs a multi-process architecture designed to isolate web content from sensitive system resources through sandboxes that restrict what code running in a tab can do. However, when an attacker compromises the renderer process of a malicious or compromised website, they are typically confined within this restrictive environment. The use-after-free condition in PowerBookmarks provided a mechanism for privilege escalation, allowing an attacker to break out of the sandbox boundary. By leveraging social engineering techniques such as tricking users into installing a crafted Chrome extension, the attacker could trigger the vulnerable code path and execute arbitrary commands with higher privileges than those granted to standard web content.
The operational impact of this vulnerability is severe, enabling remote attackers who have already achieved initial access through renderer compromise or malicious extensions to achieve full control over the victim's browser environment. This can lead to theft of sensitive data stored in cookies, local storage, and bookmarks, as well as potential lateral movement within a network if the compromised browser serves as an entry point for further attacks. The severity rating of High by the Chromium security team reflects the ease with which this exploit chain could be constructed given sufficient social engineering success and renderer compromise.
To mitigate risks associated with such vulnerabilities, organizations should ensure that all instances of Google Chrome are updated to version 157.0.8103.38 or later immediately upon availability. Additionally, implementing strict extension policies through enterprise management tools can prevent the installation of unverified or potentially malicious extensions. Users should be educated on recognizing social engineering tactics and avoiding the installation of browser add-ons from unofficial sources. From a technical standpoint, developers must adhere to secure coding practices that emphasize rigorous memory safety checks, particularly when dealing with dynamic content injection and extension APIs.
This incident aligns with Common Weakness Enumeration (CWE) identifier CWE-416, which describes Use After Free conditions where references are used after they have been freed. In the context of the MITRE ATT&CK framework, this vulnerability facilitates techniques related to Defense Evasion by allowing attackers to bypass sandbox restrictions and potentially Technique T1059 Command and Scripting Interpreter if arbitrary code execution leads to further payload deployment. Continuous monitoring for anomalous extension behavior and keeping software components up to date remain essential strategies in defending against such sophisticated exploitation vectors.