CVE-2026-87573 in Chrome
Summary
by MITRE • 09/09/2026
Improper input validation in Network in Google Chrome prior to 153.0.8010.36 allowed a remote attacker to bypass web origin policy via a crafted HTML page. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an improper input validation flaw within the network subsystem of Google Chrome, specifically affecting versions prior to 153.0.8010.36, represents a significant deviation from expected browser security boundaries. This defect allows for the bypassing of web origin policies through the exploitation of crafted HTML pages hosted by remote attackers. The core technical issue lies in how the browser processes network requests and validates their origins against the same-origin policy, which is fundamental to isolating content loaded from different sources. When input validation fails within this specific component, the browser may incorrectly associate a request with an origin that it does not actually belong to, or fail to enforce restrictions on data access between contexts that should remain isolated.
From a technical perspective, web origin policies serve as a critical security mechanism designed to prevent malicious scripts on one page from obtaining access to sensitive data on another page. This isolation is enforced through checks on the scheme, host, and port of URLs involved in cross-origin requests. In this instance, the flaw suggests that the network layer did not adequately sanitize or verify inputs related to these origin identifiers before processing them. An attacker could construct a malicious HTML page containing specific JavaScript code designed to trigger this validation failure. By leveraging browser features such as fetch API calls or XMLHttpRequests, the crafted payload can trick the engine into believing that a cross-origin request is same-origin, thereby granting unauthorized access to resources like cookies, local storage, or DOM elements belonging to other domains.
The operational impact of this vulnerability is substantial because it undermines one of the primary defenses against Cross-Site Scripting and data theft attacks. Successful exploitation allows remote attackers to read sensitive information from targeted websites without user consent or interaction beyond visiting a malicious page. This can lead to session hijacking, where an attacker steals authentication tokens stored in cookies, enabling them to impersonate legitimate users. Additionally, it facilitates the exfiltration of personal data, financial details, or proprietary content hosted on vulnerable sites. The severity is classified as medium by Chromium security standards because while it does not allow for arbitrary code execution directly, its ability to bypass isolation mechanisms makes it a potent tool for further attacks such as credential theft and unauthorized account access.
This vulnerability aligns with CWE-20 Improper Input Validation, which describes cases where software receives input but fails to verify that the inputs are structured correctly or fall within expected parameters. Furthermore, in terms of offensive security frameworks like MITRE ATT&CK, this behavior relates to techniques involving client-side evasion and data exfiltration via browser-based attacks. The exploitation vector is remote, requiring only a victim to visit a malicious webpage, which increases its potential for widespread abuse through phishing campaigns or compromised advertising networks.
Mitigation strategies primarily involve updating the Google Chrome browser to version 153.0.8010.36 or later, where these input validation checks have been corrected and strengthened. For organizations managing large fleets of devices, deploying automated patch management solutions ensures that this update is applied consistently across all endpoints. Additionally, implementing Content Security Policy headers can provide an additional layer of defense by restricting the sources from which content can be loaded, thereby reducing the attack surface even if a browser vulnerability exists. Users should also exercise caution when visiting untrusted websites and consider using security extensions that monitor for unusual network activity or origin violations. Regularly reviewing browser update notifications is essential to maintaining protection against such evolving web-based threats.