CVE-2018-6115 in Chrome
Summary
by MITRE
Inappropriate setting of the SEE_MASK_FLAG_NO_UI flag in file downloads in Google Chrome prior to 66.0.3359.106 allowed a remote attacker to potentially bypass OS malware checks via a crafted HTML page.
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Analysis
by VulDB Data Team • 07/20/2024
The vulnerability CVE-2018-6115 represents a critical security flaw in Google Chrome's handling of file downloads that stems from improper configuration of the SEE_MASK_FLAG_NO_UI flag during the download process. This issue affects Chrome versions prior to 66.0.3359.106 and demonstrates how seemingly minor flag configurations can have significant implications for system security. The vulnerability resides in the Windows operating system integration layer where Chrome's download mechanism interacts with the Windows API to manage file operations. When the SEE_MASK_FLAG_NO_UI flag is incorrectly set, it prevents the operating system from displaying standard user interface elements that typically accompany file downloads and malware detection processes. This flag configuration essentially disables the visual warnings and security prompts that Windows normally presents to users when downloading potentially unsafe files.
The technical exploitation of this vulnerability occurs when a remote attacker crafts a malicious HTML page that triggers a file download operation through Chrome's download mechanism. The crafted page contains specially designed elements that, when processed by the browser, cause Chrome to set the SEE_MASK_FLAG_NO_UI flag incorrectly during the download process. This misconfiguration effectively bypasses Windows' built-in malware detection mechanisms that would normally be triggered when downloading files from untrusted sources. The attack vector leverages the browser's interaction with the Windows operating system, specifically targeting the Windows API functions that handle file download operations and security prompts. The vulnerability operates at the intersection of browser security and operating system security controls, creating a scenario where the OS-level protections are circumvented through improper flag handling in the browser's download implementation.
The operational impact of this vulnerability extends beyond simple bypass of user warnings to potentially enabling more sophisticated attack scenarios. When malware detection mechanisms are disabled, malicious files can be downloaded and executed without the normal security checks that would alert users or block suspicious downloads. This creates a pathway for attackers to deliver malware payloads that might otherwise be detected and blocked by standard Windows security features. The vulnerability particularly affects users who rely on Windows' built-in protections, as the attack effectively neutralizes these defenses during the download phase. Security researchers have classified this as a medium to high severity issue due to its potential for enabling successful malware delivery and the relatively simple nature of the attack vector. The vulnerability demonstrates how browser vendors must carefully consider the interaction between their applications and underlying operating system security features.
Mitigation strategies for CVE-2018-6115 primarily focus on updating to the patched version of Google Chrome, specifically version 66.0.3359.106 or later. Users should ensure their browsers are running the latest stable version to receive the necessary security fixes that properly configure the SEE_MASK_FLAG_NO_UI flag during file download operations. Organizations should implement comprehensive patch management procedures to ensure all systems are updated promptly. Additionally, network administrators should consider implementing additional security layers such as web application firewalls and content filtering solutions to provide defense in depth. The vulnerability highlights the importance of proper flag management in system integration and the need for thorough testing of security-related API calls. From a compliance perspective, this vulnerability aligns with CWE-691, which addresses insufficient control flow management, and can be mapped to ATT&CK technique T1195 for Phishing and T1059 for Command and Scripting Interpreter, as attackers could leverage this vulnerability to deliver malicious payloads. Organizations should also review their security policies to ensure that browser security configurations are properly maintained and that users are educated about the risks of downloading files from untrusted sources.