CVE-2018-6097 in Chrome
Summary
by MITRE
Incorrect handling of asynchronous methods in Fullscreen in Google Chrome on macOS prior to 66.0.3359.117 allowed a remote attacker to enter full screen without showing a warning via a crafted HTML page.
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Analysis
by VulDB Data Team • 06/23/2023
The vulnerability identified as CVE-2018-6097 represents a critical security flaw in Google Chrome's implementation of fullscreen functionality on macOS operating systems. This issue specifically affects Chrome versions prior to 66.0.3359.117 and demonstrates a failure in proper permission handling for fullscreen transitions. The vulnerability stems from Chrome's inadequate validation of asynchronous method calls when processing fullscreen requests, creating a pathway for malicious actors to exploit the browser's fullscreen API without proper user consent or awareness.
The technical flaw manifests through improper state management during asynchronous operations within Chrome's fullscreen implementation. When a web page attempts to enter fullscreen mode, Chrome should typically display a user warning to confirm the transition, particularly when initiated programmatically without direct user interaction. However, the vulnerability allows attackers to bypass this security mechanism by crafting malicious HTML pages that exploit timing issues or race conditions in the asynchronous method handling. This flaw specifically impacts macOS versions where Chrome's fullscreen API does not properly validate the context in which fullscreen requests are made, enabling unauthorized transitions to fullscreen mode.
From an operational perspective, this vulnerability poses significant risks to user privacy and security. Attackers can craft deceptive web pages that automatically transition users into fullscreen mode without displaying the expected warning prompts. This behavior can be exploited for phishing attacks where malicious sites appear to be legitimate applications or services, or for creating confusing user experiences that mask malicious activities. The vulnerability essentially undermines the browser's security model by allowing unauthorized fullscreen transitions that could be used to hide malicious content or manipulate user interactions. Users may not realize they have entered fullscreen mode until it's too late, potentially leading to exploitation of other vulnerabilities or social engineering attacks.
The impact of this vulnerability aligns with CWE-665, which addresses improper initialization of a resource, and relates to ATT&CK technique T1100, which covers 'Web Shell' and related malicious web content delivery. Organizations should implement immediate mitigation strategies including mandatory browser updates to Chrome version 66.0.3359.117 or later, where the vulnerability has been addressed through proper asynchronous method handling and enhanced permission validation. Network administrators should also consider implementing browser security policies that restrict fullscreen API usage and monitor for suspicious web content that might attempt to exploit this vulnerability. The fix implemented by Google involved strengthening the validation of fullscreen transition requests and ensuring proper user consent mechanisms are enforced regardless of how the fullscreen request is initiated.
This vulnerability demonstrates the complexity of modern browser security and the challenges in maintaining proper user consent mechanisms across different operating systems and API implementations. The macOS-specific nature of the issue highlights the importance of platform-specific security considerations in browser development and the need for comprehensive testing across all supported platforms. Organizations should prioritize updating their browser environments to prevent exploitation of this and similar vulnerabilities that could compromise user security and privacy.