CVE-2025-12905 is a vulnerability identified in the Downloads component of Google Chrome on Windows platforms prior to version 140.0.7339.80. The issue stems from an inappropriate implementation that allows a remote attacker to bypass the Mark of the Web (MotW) security mechanism by delivering a specially crafted HTML page. MotW is a security feature designed to mark files downloaded from the internet as potentially unsafe, restricting their execution or access to prevent malicious activity. By bypassing MotW, an attacker can cause the browser to treat downloaded files as trusted, potentially enabling the execution of malicious content or scripts that would otherwise be blocked or sandboxed. The vulnerability is classified under CWE-346, which relates to insufficient verification of data authenticity or integrity. Exploitation requires no privileges but does require user interaction, such as opening or interacting with a maliciously crafted HTML page. The CVSS v3.1 base score is 5.4, reflecting a medium severity level with the vector indicating network attack vector, low attack complexity, no privileges required, user interaction required, and limited confidentiality and availability impacts. There are no known exploits in the wild at the time of publication, and no official patch links were provided, but updating to Chrome 140.0.7339.80 or later is the recommended remediation. This vulnerability could be leveraged in targeted phishing or drive-by download attacks to evade security controls that rely on MotW, increasing the risk of malware execution or data exposure.

For European organizations, this vulnerability poses a moderate risk primarily to Windows desktop environments where Google Chrome is widely used. The bypass of Mark of the Web can lead to downloaded files being treated as trusted, potentially allowing malicious payloads to execute with fewer restrictions. This could result in limited confidentiality impacts if sensitive data is exposed or integrity impacts if malicious files alter system or application behavior. Availability impact is also possible if malware disables or disrupts services. While exploitation requires user interaction, phishing campaigns or malicious websites could exploit this vulnerability to increase the success rate of attacks. Organizations with high reliance on Chrome for web access and those with less mature endpoint protection or user awareness programs are particularly at risk. The absence of known exploits in the wild reduces immediate urgency but does not eliminate the threat, especially as attackers may develop exploits over time. The vulnerability's medium severity suggests it should be addressed promptly to prevent escalation or chaining with other vulnerabilities.

European organizations should implement the following specific mitigations: 1) Immediately update all Google Chrome installations on Windows to version 140.0.7339.80 or later to ensure the vulnerability is patched. 2) Enforce strict endpoint security policies that include application whitelisting and behavior-based detection to identify and block suspicious file executions that bypass MotW. 3) Enhance user awareness training focusing on the risks of interacting with untrusted downloads and phishing attempts, emphasizing caution with unexpected HTML content or downloads. 4) Utilize network security controls such as web filtering and sandboxing to detect and block access to malicious websites hosting crafted HTML pages. 5) Monitor logs and alerts for unusual download or execution patterns that may indicate exploitation attempts. 6) Consider deploying browser security extensions or enterprise policies that reinforce MotW or equivalent download protections. 7) Regularly review and update incident response plans to include scenarios involving MotW bypass and related download-based attacks. These targeted actions go beyond generic advice by focusing on the specific nature of the vulnerability and its exploitation vector.