CVE-2026-87442 in Chrome
Summary
by MITRE • 09/09/2026
Confused deputy in Prerender in Google Chrome prior to 153.0.8010.36 allowed a remote attacker who had compromised the renderer process to potentially 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 Confused Deputy in Google Chrome prior to version 153.0.8010.36 represents a significant breach of browser isolation mechanisms, specifically targeting the integrity of web origin policies. This flaw resides within the Prerender component, a feature designed to optimize page load times by pre-fetching and rendering pages that users are likely to visit next. The core technical issue stems from an improper assignment of privileges or identity checks during the prerendering process, allowing a compromised renderer process to exploit this trust relationship. In typical browser architecture, each tab operates within its own sandboxed renderer process to prevent cross-site scripting attacks and other malicious activities from affecting other parts of the user's browsing session. However, when an attacker compromises one renderer through a separate vulnerability or social engineering tactic, they gain limited execution capabilities within that isolated environment. The confused deputy flaw allows this compromised renderer to trick the Prerender service into performing actions on behalf of a different origin than intended, effectively bypassing the same-origin policy which is fundamental to web security.
From an operational perspective, this vulnerability enables remote attackers to access sensitive data or perform unauthorized actions across different websites without user interaction or awareness. By crafting specific HTML pages that leverage the Prerender functionality, an attacker can manipulate the browser into treating content from a malicious origin as if it originated from a trusted target site. This bypass of web origin policy means that scripts running in the compromised renderer could potentially read cookies, local storage data, or DOM elements belonging to other domains that were being prerendered. The severity is classified as medium by Chromium security standards because while it requires an initial compromise of a renderer process, the resulting impact can be severe depending on the sensitivity of the sites involved and whether additional vulnerabilities exist in those target applications. It highlights the complexity of maintaining strict boundaries between different execution contexts within modern web browsers.
This type of vulnerability aligns closely with CWE-275, which describes the handling of incorrect security permissions or privileges often referred to as a confused deputy attack. In the context of browser architecture, it also relates to CWE-862, where missing authorization checks allow unauthorized access to resources. Furthermore, from an offensive cybersecurity framework perspective, this behavior is consistent with techniques found in MITRE ATT&CK under privilege escalation and defense evasion categories, specifically those involving process injection or manipulation of legitimate system processes for malicious purposes. The attacker leverages the browser's own optimization features against itself, turning a performance-enhancing mechanism into a vector for lateral movement within the user's browsing session.
Mitigation strategies primarily involve updating to Google Chrome version 153.0.8010.36 or later, where these logic errors in the Prerender component have been addressed through stricter validation of origin contexts and enhanced isolation between prerendered content and active tabs. Administrators should ensure that automatic updates are enabled for all endpoints running affected versions to minimize exposure windows. Additionally, users can reduce risk by disabling unnecessary browser features such as preloading or prefetching if they operate in high-security environments where even minor privilege escalation risks are unacceptable. Security teams should also monitor for indicators of compromise related to renderer process anomalies and enforce strict content security policies on web applications to limit the potential impact if a similar vulnerability is exploited in the future. Regular patch management remains the most effective defense against such logic-based vulnerabilities that exploit trusted relationships between browser components.