CVE-2026-121048 in Chrome
Summary
by MITRE • 11/03/2026
Race condition in V8 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: Medium)
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified as a race condition within the V8 JavaScript engine, which powers Google Chrome prior to version 157.0.8103.38, represents a critical flaw in how concurrent operations are managed during memory allocation and type checking processes. Race conditions occur when the behavior of software depends on the relative timing of uncontrollable events, such as thread scheduling or network packet arrival. In this specific instance, the V8 engine failed to properly synchronize access to shared resources during garbage collection or property optimization phases. This lack of synchronization allowed a crafted HTML page, served from a malicious website, to trigger a state where an object's type information was modified concurrently with its usage by another thread or execution context. The attacker could exploit this window of inconsistency to manipulate the internal representation of objects in memory, effectively bypassing V8’s strict type safety mechanisms that are designed to prevent out-of-bounds accesses and other memory corruption errors.
From a technical perspective, this flaw falls under the category of CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization Race Condition Vulnerability. The exploitation mechanism relies on the attacker constructing a complex JavaScript payload that forces the browser into a specific execution state where race conditions are highly probable. By carefully timing memory allocations and deallocations, combined with precise manipulation of object properties, an adversary can cause V8 to misinterpret the layout or type of an object in heap memory. This misinterpretation leads to arbitrary read and write capabilities within the sandboxed environment of the browser renderer process. Although Chrome employs a multi-process architecture that isolates web content from the operating system kernel, breaking out of this isolation through precise memory corruption techniques remains a significant threat vector for advanced persistent threats and state-sponsored actors seeking initial access or privilege escalation on compromised systems.
The operational impact of successfully exploiting this vulnerability is severe, as it allows remote code execution with the privileges of the current user within the browser sandbox. While the sandbox provides substantial protection against direct system compromise, achieving arbitrary code execution inside the renderer process enables attackers to perform further exploitation steps such as sandbox escapes, data exfiltration from other tabs or applications sharing the same profile, and installation of malware that persists beyond the browsing session. The Chromium security team has classified this issue with a Medium severity rating, reflecting the complexity required for reliable exploitation versus the high impact if successful. This classification underscores the importance of timely patching even for vulnerabilities deemed less critical than use-after-free or buffer overflow issues, as race conditions can be particularly difficult to detect in automated testing environments and may only manifest under specific load conditions or hardware configurations.
Mitigation strategies primarily involve updating Google Chrome to version 157.0.8103.38 or later, where the synchronization primitives within V8 have been strengthened to prevent these race conditions from occurring. For organizations unable to immediately patch all endpoints, implementing strict content security policies and restricting JavaScript execution on untrusted domains can reduce the attack surface. Additionally, deploying browser isolation solutions or web filtering services that block access to known malicious sites provides an effective layer of defense against drive-by exploitation attempts. Security teams should also monitor for indicators of compromise related to unusual memory usage patterns in Chrome processes, as these may signal active exploitation attempts targeting this vulnerability. Continuous monitoring and adherence to industry standards such as the MITRE ATT&CK framework, specifically mapping this event to techniques involving initial access via spearphishing links or drive-by downloads followed by execution within a sandboxed environment, will aid in detecting and responding to potential incidents effectively.