CVE-2026-121129 in Chrome
Summary
by MITRE • 11/03/2026
Use after free in WebRTC in Google Chrome prior to 157.0.8103.38 allowed a remote attacker to execute arbitrary code inside the sandbox via a crafted HTML page. (Chromium security severity: High)
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Analysis
by VulDB Data Team • 11/04/2026
The vulnerability identified as a use-after-free flaw within the WebRTC component of Google Chrome prior to version 157.0.8103.38 represents a critical memory management error that compromises the integrity and confidentiality of the user environment. This specific class of vulnerabilities occurs when a program continues to use a pointer after it has been freed, leading to undefined behavior that can be exploited by malicious actors. In this instance, the flaw resides in the complex media handling logic inherent to WebRTC, which manages real-time audio, video, and data communication streams directly within the browser sandbox. The presence of such an error indicates a failure in reference counting or object lifecycle management during the processing of networked media packets or signaling messages.
A remote attacker can exploit this vulnerability by hosting or distributing a specially crafted HTML page that triggers the erroneous memory access conditions when loaded by a victim using an affected version of Chrome. Upon loading, the malicious script interacts with WebRTC APIs in a manner that causes specific internal objects to be deallocated while still being referenced elsewhere in the application's execution context. When the program subsequently attempts to dereference these dangling pointers, it accesses freed memory regions which may contain attacker-controlled data or allow for arbitrary code execution primitives. This exploitation vector is particularly dangerous because WebRTC operates with significant privileges relative to other browser components due to its need for direct hardware access and low-latency processing capabilities.
The operational impact of this vulnerability is severe, as successful exploitation allows a remote attacker to execute arbitrary code within the context of the Chrome sandbox. While modern browsers employ robust sandboxing mechanisms designed to limit the damage caused by such exploits, achieving code execution inside the sandbox significantly increases the risk of further privilege escalation attacks. An attacker could potentially bypass security controls, exfiltrate sensitive user data, install persistent malware, or use the compromised browser as a pivot point for attacking other systems on the local network. The high severity rating assigned by Chromium reflects the ease with which this memory corruption can be triggered and its potential to lead to full system compromise if sandbox escape techniques are combined with this initial foothold.
From a classification perspective, this vulnerability aligns closely with CWE-416, Use After Free, which describes situations where an application uses a pointer after it has been freed or deallocated. This often leads to crashes, data corruption, or arbitrary code execution depending on how the memory is reused and what state the system is in at that moment. In terms of offensive security frameworks such as MITRE ATT&CK, this vulnerability facilitates initial access through technique T1189 Drive-by Compromise, where users are tricked into visiting a malicious website. The exploitation phase leverages techniques associated with execution within constrained environments, potentially leading to defense evasion if the attacker attempts to hide their presence or escalate privileges beyond the browser sandbox boundaries.
Mitigation for this vulnerability primarily involves updating Google Chrome to version 157.0.8103.38 or later, where these memory management issues have been addressed through rigorous code reviews and automated fuzzing efforts. Organizations should ensure that endpoint protection solutions are configured to detect anomalous behavior associated with browser-based exploits, such as unusual network connections initiated by the Chrome process or attempts to access sensitive files outside standard directories. Additionally, users can reduce their attack surface by disabling WebRTC if it is not required for their specific use cases, although this may impact functionality of legitimate web applications that rely on real-time communication features. Regular patching cycles and monitoring for browser update notifications remain the most effective defense against such memory corruption vulnerabilities in widely used software components.