CVE-2025-5064 is a medium-severity vulnerability affecting Google Chrome versions prior to 137.0.7151.55. The flaw lies in the inappropriate implementation of the Background Fetch API, which is designed to allow web applications to fetch large amounts of data in the background, even after the user navigates away from the page. Due to this implementation issue, a remote attacker can craft a malicious HTML page that exploits the Background Fetch API to leak cross-origin data. This means that the attacker can bypass the same-origin policy, a fundamental web security mechanism that normally prevents a web page from accessing data from another domain. The vulnerability is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor), indicating that it allows unauthorized disclosure of information. The CVSS v3.1 base score is 5.4, reflecting a medium severity level. The vector string (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N) indicates that the attack can be performed remotely over the network with low attack complexity, requires no privileges, but does require user interaction (such as visiting a malicious page). The impact affects confidentiality and integrity to a limited extent, with no impact on availability. No known exploits are currently reported in the wild, and no official patch links are provided yet, suggesting that the vulnerability was recently disclosed. Overall, this vulnerability allows an attacker to leak sensitive data across origins via a crafted webpage, potentially exposing user information or session data that should be isolated by browser security policies.

For European organizations, this vulnerability poses a risk primarily to the confidentiality of sensitive information accessed via Google Chrome. Since Chrome is widely used across enterprises, government agencies, and critical infrastructure sectors in Europe, the ability to leak cross-origin data could lead to unauthorized disclosure of confidential business information, user credentials, or session tokens. This could facilitate further attacks such as account takeover, espionage, or data theft. The requirement for user interaction means that phishing or social engineering campaigns could be used to lure victims to malicious pages. Sectors with high reliance on web applications and sensitive data, such as finance, healthcare, and public administration, are particularly at risk. Although the vulnerability does not affect system availability or integrity directly, the confidentiality breach could undermine trust and compliance with data protection regulations like GDPR. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits once the vulnerability details become widely known.

European organizations should prioritize updating Google Chrome to version 137.0.7151.55 or later as soon as it becomes available to ensure the vulnerability is patched. Until an official patch is released, organizations should implement the following mitigations: 1) Educate users about the risks of visiting untrusted or suspicious websites to reduce the likelihood of successful phishing attacks exploiting this vulnerability. 2) Employ web filtering solutions to block access to known malicious domains and suspicious URLs that could host crafted HTML pages exploiting this flaw. 3) Use Content Security Policy (CSP) headers to restrict the sources from which scripts and resources can be loaded, limiting the attack surface. 4) Monitor network traffic for unusual outbound requests that could indicate exploitation attempts. 5) Consider deploying browser isolation or sandboxing technologies to contain potential malicious activity within the browser environment. 6) Coordinate with IT and security teams to ensure rapid deployment of patches once available and to maintain up-to-date threat intelligence on this vulnerability.