CVE-2026-106384 in Chrome
Summary
by MITRE • 10/07/2026
Missing authorization in SiteIsolation in Google Chrome prior to 155.0.8059.39 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified as missing authorization within the SiteIsolation mechanism of Google Chrome prior to version 155.0.8059.39 represents a critical failure in browser-based process separation logic. Site Isolation is a fundamental security architecture designed to prevent cross-site scripting attacks and data theft by ensuring that each site runs in its own unique renderer process, thereby isolating sensitive web content from potentially malicious code hosted on different origins. This specific flaw arises when the authorization checks governing inter-process communication or state transitions are insufficiently validated, allowing an attacker who has already achieved partial compromise of a renderer process to manipulate internal browser states without proper permission verification. The core technical deficiency lies in the failure to enforce strict origin-based access controls during critical operations that maintain isolation boundaries, effectively creating a logical gap where malicious scripts can execute commands or access resources outside their designated sandboxed environment.
From an operational perspective, this vulnerability allows for a significant escalation of privilege within the browser context. An attacker who has successfully exploited a separate vulnerability to gain code execution within a renderer process can leverage this authorization bypass to break out of that isolated container. By crafting a specific HTML page or script payload, the adversary can trigger actions that circumvent the site isolation policies, potentially accessing data from other tabs, extensions, or even higher-privilege processes such as the browser utility or GPU processes depending on the exact implementation details of the flaw. This undermines one of Chrome's primary defenses against cross-site scripting and side-channel attacks like Spectre variants, which rely on process separation to mitigate information leakage between different web contexts.
The security severity is classified as medium by Chromium standards because while it does not provide direct arbitrary code execution from a clean state, it significantly lowers the barrier for attackers who have already achieved initial access through other means such as drive-by downloads or malicious advertisements. The ability to bypass site isolation expands the attack surface considerably, allowing for more persistent and impactful data exfiltration strategies that were previously blocked by process boundaries. This aligns with Common Weakness Enumeration CWE-269, which describes Improper Privilege Assignment, specifically in contexts where a user or program is given privileges it should not possess to perform its intended function securely. Furthermore, this behavior maps directly to the MITRE ATT&CK technique T1055.013, Process Injection via Browser Extension APIs, and potentially T1218.014, Signed Binary Proxy Execution involving browser processes, as the attacker utilizes legitimate system mechanisms in an unauthorized manner to achieve lateral movement within the client environment.
Mitigation for this vulnerability requires immediate updates to Google Chrome on all affected platforms to version 155.0.8059.39 or later, where the authorization checks have been hardened and validated against edge cases that previously allowed bypasses. Organizations should enforce automated patch management policies to ensure rapid deployment of security fixes across enterprise fleets. Additionally, administrators can implement Content Security Policy headers with strict frame-ancestors directives to add a layer of defense-in-depth, although this does not replace the need for binary updates as it only mitigates certain framing attacks rather than process isolation flaws. Continuous monitoring for anomalous browser behavior and restricting the installation of unverified extensions further reduces the risk profile associated with renderer compromise attempts that might attempt to exploit such authorization gaps.