CVE-2026-106271 in Chrome
Summary
by MITRE • 10/06/2026
Missing authorization in Workers 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 PDF file. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 10/07/2026
The vulnerability identified as missing authorization within the Workers component of Google Chrome prior to version 155.0.8059.39 represents a significant breach in the browser's multi-process architecture, specifically targeting the isolation mechanisms designed to prevent cross-site data leakage. This flaw allows a remote attacker who has already achieved code execution within a renderer process to escalate their privileges and bypass site isolation controls. The core technical issue stems from an improper validation of authorization checks when handling worker threads, which are essential for executing JavaScript in background tasks separate from the main UI thread. By exploiting this gap through a crafted PDF file, an attacker can manipulate the browser's internal state to trick the engine into granting unauthorized access between contexts that should remain strictly separated by origin boundaries.
Site isolation is a critical security feature implemented by Chromium-based browsers to mitigate attacks such as Spectre and other side-channel exploits that rely on reading memory from different sites within the same process. When site isolation functions correctly, it ensures that data from one website cannot be accessed by another, even if they are loaded in separate tabs or frames of the same browser window. The vulnerability described here undermines this fundamental guarantee. Because the authorization check is missing during specific worker operations, an attacker can leverage a maliciously constructed PDF document to trigger code paths where these checks are bypassed. This effectively collapses the security boundary between different origins, allowing the compromised renderer process to read sensitive data from other sites or execute actions on behalf of those sites without proper authentication.
The operational impact of this vulnerability is severe due to its potential for remote exploitation via a simple vector like a PDF file. An attacker does not need physical access or complex social engineering beyond convincing a user to open the malicious document. Once opened, the crafted content can exploit the flaw in real-time, leading to unauthorized data exfiltration, session hijacking, or further lateral movement within the victim's environment if other services are accessible from the compromised context. The Chromium security team has classified this issue with a medium severity rating, reflecting its potential for remote code execution and privilege escalation under specific conditions where site isolation is relied upon as the primary defense layer against cross-site attacks.
To mitigate the risks associated with this vulnerability, users must ensure that their Google Chrome installation is updated to version 155.0.8059.39 or later immediately. This update contains the necessary patches to enforce proper authorization checks within the Workers component, thereby restoring the integrity of site isolation mechanisms. Additionally, organizations should consider implementing strict content security policies and disabling unnecessary features such as PDF viewing in browsers if feasible, to reduce the attack surface presented by document-based exploits. Regular patch management cycles are essential to address such vulnerabilities promptly before they can be weaponized at scale in the wild.
From a classification perspective, this vulnerability aligns with CWE-269, which denotes Improper Privilege Management, as it involves an actor obtaining privileges or access that they should not have due to insufficient authorization checks. Furthermore, the exploitation technique relates to ATT&CK tactic T1053, specifically Scheduled Task/Job, in the context of leveraging system processes like workers for malicious purposes, although more broadly it falls under privilege escalation techniques within browser environments. Understanding these mappings helps security teams prioritize remediation efforts and monitor for indicators of compromise that match this specific exploitation pattern involving PDF files and renderer process compromises.