CVE-2026-87543 in Chrome
Summary
by MITRE • 09/09/2026
Missing authorization in Core in Google Chrome prior to 153.0.8010.36 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted HTML page. (Chromium security severity: Low)
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as missing authorization within the core components of Google Chrome prior to version 153.0.8010.36 represents a critical failure in access control mechanisms that underpin browser security architecture. This flaw specifically impacts site isolation, a fundamental defense mechanism designed to prevent cross-site scripting and data theft by ensuring that resources from different origins are kept strictly separate within distinct processes. When authorization checks are omitted or improperly implemented during the handling of specific internal requests or state transitions, it creates an avenue for privilege escalation at the process level rather than just the user interface level. This type of issue is categorized under CWE-269, which denotes Improper Privilege Assignment, as the browser fails to correctly restrict actions based on the security context of the caller.
The operational impact of this vulnerability centers on the ability of a remote attacker to bypass site isolation protections through a crafted HTML page. Site isolation relies heavily on the assumption that renderer processes cannot access or influence data belonging to other sites without explicit and verified authorization. By exploiting the missing authorization check, an attacker who has already compromised a renderer process can manipulate internal browser states to interact with resources from different origins as if they were part of their own site context. This effectively neutralizes one of Chrome's most robust defenses against cross-site attacks, allowing for potential data exfiltration or further lateral movement within the user's browsing session. The Chromium security severity is rated as Low because while the bypass is technically possible, it requires a pre-existing compromise of the renderer process, which itself is difficult to achieve without prior exploitation of other vulnerabilities such as sandbox escapes or remote code execution flaws in extensions or plugins.
From an offensive security perspective, this vulnerability aligns with techniques observed in the MITRE ATT&CK framework, particularly those related to Defense Evasion and Credential Access via Browser Hacks. Attackers often seek to bypass isolation mechanisms to maintain persistence or escalate privileges after initial access is gained through phishing or drive-by downloads. The ability to circumvent site isolation means that sensitive information such as cookies, local storage data, or session tokens from other tabs could potentially be accessed by the malicious renderer process. This undermines the principle of least privilege and compromises the integrity of the user's browsing environment, even if the initial entry point was limited in scope.
Mitigation for this vulnerability requires immediate updating to Google Chrome version 153.0.8010.36 or later, where the authorization checks have been properly implemented within the core components. Administrators should ensure that automatic updates are enabled to prevent exposure during the window of vulnerability. For environments where automatic updates cannot be deployed immediately, manual patching is essential. Additionally, users can employ browser extensions that enforce stricter content security policies or utilize sandboxed browsing profiles for untrusted activities to reduce the attack surface available to renderer processes. Continuous monitoring for unusual process behavior and network connections originating from browser child processes can also help in detecting potential exploitation attempts before significant damage occurs.