Description
A cookie encryption bypass vulnerability exists in Google Chrome’s AppBound mechanism due to weak path validation logic within the elevation service. When Chrome encrypts a cookie key, it records its own executable path as validation metadata. Later, when decrypting, the elevation service compares the requesting process’s path to this stored path. However, due to path canonicalization inconsistencies, an attacker can impersonate Chrome (e.g., by naming their binary chrome.exe and placing it in a similar path) and successfully retrieve the encrypted cookie key. This allows malicious processes to retrieve cookies intended to be restricted to the Chrome process only. Confirmed in Google Chrome with AppBound Encryption enabled. Other Chromium-based browsers may be affected if they implement similar COM-based encryption mechanisms.
EPSS Score:
0%
Comprehensive Technical Analysis of EUVD-2025-19757
1. Vulnerability Assessment and Severity Evaluation
The vulnerability described in EUVD-2025-19757 pertains to a cookie encryption bypass in Google Chrome’s AppBound mechanism. This flaw arises from weak path validation logic within the elevation service, allowing an attacker to impersonate Chrome and retrieve encrypted cookie keys. The severity of this vulnerability is significant, as indicated by its CVSS base score of 9.3. This high score reflects the potential for high confidentiality, integrity, and availability impacts, as well as the ease of exploitation under certain conditions.
CVSS Vector Breakdown:
- AV:L (Local Access Vector): The attacker requires local access to the system.
- AC:L (Low Attack Complexity): The attack does not require specialized conditions or knowledge.
- AT:N (No Authentication): No authentication is required to exploit the vulnerability.
- PR:L (Low Privileges Required): The attacker needs low-level privileges to exploit the vulnerability.
- UI:N (No User Interaction): No user interaction is required for the attack to succeed.
- VC:H, VI:H, VA:H (High Impact on Confidentiality, Integrity, and Availability): The vulnerability has a high impact on all three security aspects.
- SC:H, SI:H, SA:H (High Impact on Confidentiality, Integrity, and Availability Scope): The scope of the impact is high across all security dimensions.
2. Potential Attack Vectors and Exploitation Methods
An attacker with local access to a system running a vulnerable version of Google Chrome can exploit this vulnerability by:
- Binary Impersonation: Naming their malicious binary
chrome.exeand placing it in a path similar to the legitimate Chrome executable. - Path Canonicalization Inconsistencies: Exploiting the inconsistencies in path canonicalization to bypass the path validation logic.
- Retrieving Encrypted Cookie Keys: Successfully retrieving the encrypted cookie keys, which are intended to be restricted to the Chrome process only.
This allows the attacker to access sensitive cookies, potentially leading to unauthorized access to user sessions, data theft, and other malicious activities.
3. Affected Systems and Software Versions
The vulnerability is confirmed to affect Google Chrome versions 127 through 128 with AppBound Encryption enabled. Other Chromium-based browsers may also be affected if they implement similar COM-based encryption mechanisms. Users and organizations running these versions should prioritize updating to a patched version as soon as possible.
4. Recommended Mitigation Strategies
To mitigate the risk associated with this vulnerability, the following strategies are recommended:
- Update Software: Immediately update Google Chrome to the latest version that includes a fix for this vulnerability.
- Restrict Local Access: Limit local access to trusted users and implement strict access controls.
- Monitor for Suspicious Activity: Use security monitoring tools to detect and respond to any suspicious activity that may indicate an attempt to exploit this vulnerability.
- Implement Application Whitelisting: Use application whitelisting to prevent unauthorized binaries from executing.
- Regular Security Audits: Conduct regular security audits to identify and address potential vulnerabilities in the system.
5. Impact on European Cybersecurity Landscape
The impact of this vulnerability on the European cybersecurity landscape is substantial. Given the widespread use of Google Chrome and Chromium-based browsers, a successful exploit could lead to widespread data breaches and unauthorized access to sensitive information. This underscores the importance of timely patching and robust security measures to protect against such vulnerabilities.
6. Technical Details for Security Professionals
Path Validation Logic:
- The vulnerability stems from inconsistencies in how the elevation service validates the executable path during the decryption process.
- The attacker can exploit these inconsistencies by placing a malicious binary in a path that the validation logic incorrectly recognizes as legitimate.
Encryption Mechanism:
- The AppBound mechanism in Google Chrome uses COM-based encryption to protect cookie keys.
- The flaw allows an attacker to bypass this encryption, retrieving the keys and accessing the cookies.
Detection and Response:
- Security professionals should implement endpoint detection and response (EDR) solutions to monitor for unusual process activity, especially related to Chrome executables.
- Regularly review and update security policies to ensure that only trusted applications are allowed to run on critical systems.
Patch Management:
- Ensure that all systems are updated to the latest version of Google Chrome that addresses this vulnerability.
- Regularly review and apply security patches for all software in use within the organization.
By understanding the technical details and implementing the recommended mitigation strategies, security professionals can effectively protect against this vulnerability and maintain the integrity of their systems.