CVE-2026-121250 in Chrome
Summary
by MITRE • 11/03/2026
Use after free in Extensions in Google Chrome prior to 157.0.8103.38 allowed a remote attacker leveraging social engineering to potentially 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 as a use-after-free condition within Google Chrome's extensions subsystem represents a critical memory management flaw that compromises the integrity of the browser's execution environment prior to version 157.0.8103.38. This specific class of error occurs when an extension attempts to access or manipulate a pointer after the underlying memory it references has already been freed by the system. In modern web browsers, extensions operate within a restricted context known as the sandbox, which is designed to limit their permissions and prevent them from accessing sensitive data or executing arbitrary code on the host machine. However, when a use-after-free vulnerability exists in this layer, an attacker can craft malicious JavaScript or extension components that trigger the premature deallocation of memory objects while references to those objects are still held active by other parts of the browser process.
The technical mechanism behind this exploitation involves manipulating the lifecycle of internal data structures used by Chrome extensions. When a developer creates an object and subsequently deletes it, but fails to nullify all pointers referencing that object, any subsequent access to these dangling pointers results in undefined behavior. In the context of Google Chrome, attackers can leverage social engineering techniques to persuade users to install or interact with a maliciously crafted extension. Once executed, this extension can trigger specific sequences of events that cause the browser to free memory associated with an internal component while maintaining active references to it. By carefully controlling the timing and content of subsequent allocations, an attacker can overwrite the freed memory region with controlled data structures, effectively gaining control over the program counter or critical function pointers within the Chrome process.
This flaw allows for potential arbitrary code execution outside the sandbox boundary, which is a severe escalation of privilege from a web context to the operating system level. The operational impact is significant because it bypasses multiple layers of security controls including site isolation and content security policies that are intended to contain threats within isolated frames or processes. An attacker who successfully exploits this vulnerability can execute arbitrary commands on the victim's machine, leading to full system compromise. This includes the ability to steal sensitive information such as cookies, passwords, and session tokens stored by the browser, install additional malware, or use the compromised device as part of a botnet. The severity is rated as High due to the ease with which social engineering can be employed to deliver the exploit vector through seemingly legitimate extension stores or phishing campaigns disguised as useful tools.
From an industry standard perspective, this vulnerability aligns closely with CWE-416, Use After Free, which describes errors resulting from accessing memory after it has been freed. It also maps to MITRE ATT&CK techniques related to initial access via trusted software domains and subsequent privilege escalation through exploitation of application vulnerabilities. The attack path typically involves the adversary leveraging valid credentials or user trust to introduce malicious code into a protected environment, followed by exploiting logic errors in that environment's memory management routines to break out of confinement restrictions.
Mitigation strategies for this vulnerability primarily involve immediate patching of Google Chrome to version 157.0.8103.38 or later, where the underlying memory management issues have been addressed through stricter pointer validation and lifecycle tracking mechanisms. Organizations should enforce strict policies regarding the installation of third-party extensions, limiting them to approved sources only. Additionally, enabling automatic updates ensures that users receive security patches promptly as they are released. Security awareness training is also critical to reduce the success rate of social engineering attacks that serve as the delivery mechanism for such exploits. Monitoring browser logs for unusual extension behavior or memory access patterns can provide early detection indicators in environments where patching might be delayed, although proactive prevention through software updates remains the most effective defense against this class of vulnerability.