CVE-2025-34090 is a critical security vulnerability affecting Google Chrome version 127, specifically targeting the AppBound cookie encryption mechanism. The flaw arises from an untrusted search path issue (CWE-426) combined with insufficient validation of COM server paths during inter-process communication. In this scenario, a local attacker with low privileges can hijack the COM class identifier (CLSID) registration used by Chrome's elevation service. By redirecting this registration to a non-existent or malicious binary, Chrome silently reverts to a legacy cookie encryption method that relies solely on user-level Data Protection API (DPAPI) protections. This fallback weakens the encryption, allowing any malware operating under the same user context to decrypt browser cookies without requiring SYSTEM-level privileges. Since cookies often contain sensitive session tokens and authentication data, this vulnerability effectively bypasses the enhanced security model intended by AppBound encryption, exposing users to session hijacking and credential theft. While confirmed in Google Chrome, other Chromium-based browsers that implement similar COM-based encryption mechanisms may also be vulnerable. The vulnerability has a CVSS 4.0 base score of 9.3, indicating critical severity, with attack vector local, low attack complexity, no user interaction, and requiring low privileges. No known exploits are currently reported in the wild, but the potential impact is significant given the sensitive nature of cookie data and the ease of exploitation by local malware.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of user sessions and credentials stored in Chromium-based browsers. Since cookies often facilitate single sign-on and maintain authenticated sessions for enterprise web applications, their compromise could lead to unauthorized access to corporate resources, internal portals, and cloud services. The attack requires local access but only low privileges, meaning that malware or insider threats could exploit this flaw to escalate their capabilities without needing SYSTEM-level access. This is particularly concerning in environments where endpoint security is lax or where users frequently install untrusted software. The silent fallback to weaker encryption means that detection may be difficult, increasing the risk of prolonged undetected breaches. Given the widespread use of Google Chrome and Chromium browsers in European enterprises, including sectors such as finance, healthcare, and government, the vulnerability could facilitate lateral movement and data exfiltration. Moreover, organizations subject to strict data protection regulations like GDPR must consider the potential compliance and reputational impacts of cookie theft leading to personal data exposure.

To mitigate this vulnerability, European organizations should prioritize the following actions: 1) Immediate deployment of security patches from Google once available; since no patch links are currently provided, organizations should monitor official Google security advisories closely. 2) Implement application whitelisting and restrict the ability of low-privileged users to register or modify COM class identifiers, thereby preventing hijacking attempts. 3) Enhance endpoint detection and response (EDR) capabilities to monitor for suspicious modifications to COM registrations or unexpected fallback to legacy encryption mechanisms. 4) Enforce strict privilege separation and limit local user permissions to reduce the attack surface for local malware. 5) Educate users about the risks of installing untrusted software and maintain robust anti-malware defenses to prevent local compromise. 6) Consider deploying browser security policies that restrict or disable legacy encryption fallbacks if configurable. 7) Conduct regular audits of COM registrations and inter-process communication paths on critical systems. These targeted measures go beyond generic advice by focusing on the specific attack vector of COM hijacking and the fallback encryption weakness.