CVE-2026-87469 in Chrome
Summary
by MITRE • 09/09/2026
Improper input validation in Extensions in Google Chrome prior to 153.0.8010.36 allowed a remote attacker to bypass web origin policy into a privileged page via crafted network traffic. (Chromium security severity: Low)
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an improper input validation flaw within the Extensions subsystem of Google Chrome prior to version 153.0.8010.36 represents a significant breach in browser isolation mechanisms. This defect specifically affects how the browser processes network traffic associated with installed extensions, which operate under elevated privileges compared to standard web pages. The core technical issue lies in the failure to adequately sanitize or validate inputs received through crafted network requests before they are processed by privileged extension contexts. When an attacker constructs specific malicious network packets designed to exploit this validation gap, the browser incorrectly interprets these external signals as legitimate internal commands originating from a trusted source. This misinterpretation allows the attacker to manipulate the execution flow within the extension environment in ways that were not intended by the developers.
The operational impact of this vulnerability is primarily centered on the bypassing of web origin policies, which are fundamental security boundaries designed to prevent malicious scripts from accessing data across different domains or origins. By exploiting this flaw, a remote attacker can effectively bridge the gap between an untrusted external network context and a privileged internal page within Chrome. This means that code executed in a less-privileged environment gains unauthorized access to sensitive information or functionality reserved for higher-privilege contexts. The severity is classified as low by Chromium security standards because while the isolation boundary is breached, the practical exploitation requires specific conditions regarding how extensions are configured and which network vectors are accessible to the attacker. However, even with a low classification, such bypasses can lead to data exfiltration or unauthorized actions if combined with other vulnerabilities in extension code.
From a threat modeling perspective, this vulnerability aligns closely with CWE-20 Improper Input Validation, as the root cause is the acceptance of untrusted data without sufficient checks on its format, content, or origin. Furthermore, it relates to ATT&CK technique T1537 Transfer Data over Command and Control Channel, where attackers use established communication channels for malicious purposes, although in this case, the channel itself becomes a vector for privilege escalation within the browser sandbox. The attack scenario typically involves an attacker hosting a malicious webpage or manipulating network traffic that interacts with Chrome extensions via their exposed APIs or background scripts. If successful, the attacker can read cookies, local storage data, or perform actions on behalf of the user in contexts where such access should be strictly prohibited by same-origin policies.
Mitigation strategies for this vulnerability are primarily focused on software updates and configuration hardening. The most effective remediation is to upgrade Google Chrome to version 153.0.8010.36 or later, which includes patches that enforce stricter input validation rules within the extension processing pipeline. Administrators should ensure automatic update policies are enabled for all endpoints running this browser to prevent exposure during window periods where older versions remain in use. Additionally, users and organizations should audit installed extensions, removing any that are unnecessary or from untrusted publishers, as reducing the attack surface minimizes the potential impact of such isolation bypasses. Implementing Content Security Policy headers within extension pages can also provide an additional layer of defense by restricting how resources are loaded and executed, thereby limiting the effectiveness of crafted network traffic even if input validation fails.