CVE-2026-121128 in Chrome
Summary
by MITRE • 11/03/2026
Use after free in Scheduling 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 • 11/04/2026
The vulnerability identified as a use-after-free error within the scheduling subsystem of Google Chrome prior to version 157.0.8103.38 represents a critical memory management flaw that can be leveraged by remote attackers to achieve arbitrary code execution. This specific class of bug occurs when a program continues to use a pointer after the memory it points to has been freed, often leading to undefined behavior that security researchers and exploit developers frequently target for privilege escalation or sandbox escape. In this instance, the defect resides in the browser's internal scheduling mechanisms, which manage how tasks are queued and executed within the rendering process. When an attacker crafts a malicious HTML page containing specific JavaScript sequences designed to trigger rapid allocation and deallocation cycles around these scheduled objects, they can manipulate the state of freed memory blocks before they are reallocated for legitimate purposes.
From a technical perspective, this vulnerability aligns with CWE-416, which classifies use-after-free errors as situations where an application uses memory after it has been freed. The operational impact is severe because Chrome relies heavily on sandboxing to isolate web content from the underlying operating system and user data. By exploiting this flaw through a crafted HTML page served via a website or embedded in phishing materials, an attacker can corrupt internal browser structures such as function pointers or object vtables. This corruption allows the execution of arbitrary shellcode within the context of the renderer process. Although Chrome employs multiple layers of defense including DEP and ASLR, successful exploitation of this use-after-free condition can potentially bypass these mitigations to escape the sandbox boundary, thereby granting the attacker control over the browser's processes with limited privileges that could be further escalated depending on system configurations.
This incident is also relevant to MITRE ATT&CK framework techniques related to initial access and execution, specifically those involving web-based attacks such as Drive-by Code Execution (T1189). The medium severity rating assigned by Chromium indicates that while the vulnerability is significant enough to allow code execution, it may require specific conditions or user interaction beyond simple page load in some contexts, though modern exploit chains often automate these interactions seamlessly. To mitigate this risk, users must ensure their browsers are updated to version 157.0.8103.38 or later where the memory management logic for scheduling tasks has been patched to prevent access to deallocated objects. Additionally, organizations should enforce strict content security policies and utilize browser hardening features that restrict script execution from untrusted sources to reduce the attack surface available to such exploits.