CVE-2018-4190 in iOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.4 is affected. Safari before 11.1.1 is affected. iCloud before 7.5 on Windows is affected. iTunes before 12.7.5 on Windows is affected. tvOS before 11.4 is affected. The issue involves the "WebKit" component. It allows remote attackers to obtain sensitive credential information that is transmitted during a CSS mask-image fetch.
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Analysis
by VulDB Data Team • 03/21/2023
The vulnerability identified as CVE-2018-4190 represents a critical security flaw within Apple's WebKit rendering engine that affects multiple operating systems and applications. This issue specifically targets the CSS mask-image functionality within WebKit, creating an unexpected information disclosure channel that could potentially expose sensitive credential data during web browsing operations. The vulnerability impacts iOS versions prior to 11.4, Safari versions before 11.1.1, iCloud applications on Windows before version 7.5, iTunes on Windows before version 12.7.5, and tvOS versions before 11.4, demonstrating the widespread nature of this WebKit-based flaw.
The technical implementation of this vulnerability exploits the way WebKit handles CSS mask-image properties when fetching external resources. When a web page attempts to use a CSS mask-image that references an external resource, the browser's handling of this operation inadvertently leaks credential information that should remain confidential. This occurs because the mask-image fetch operation does not properly sanitize or isolate the credential context, allowing attackers to potentially capture authentication tokens, session identifiers, or other sensitive data that may be present in the HTTP headers or cookies associated with the resource fetch. The flaw operates at the protocol level where WebKit's resource fetching mechanism fails to maintain proper separation between different credential contexts.
The operational impact of CVE-2018-4190 extends beyond simple information disclosure, as it creates opportunities for attackers to perform credential harvesting attacks against users of affected Apple products. Remote attackers can craft malicious web pages that leverage this vulnerability to capture sensitive information transmitted during CSS mask-image fetch operations, potentially enabling session hijacking, account takeovers, or other credential-based attacks. This vulnerability particularly affects users of web-based applications and services that rely on proper credential isolation, making it especially dangerous in environments where users access multiple authenticated services through the same browser session. The cross-platform nature of the vulnerability means that attackers could potentially exploit it across different Apple ecosystems, from mobile devices to desktop applications.
Security mitigations for this vulnerability primarily involve updating affected systems to patched versions of the respective software components. Apple released updates for iOS 11.4, Safari 11.1.1, iCloud 7.5, iTunes 12.7.5, and tvOS 11.4 that address the WebKit implementation flaw. Organizations should implement immediate patch management procedures to ensure all affected devices and applications are updated. Additionally, network administrators should monitor for suspicious web traffic patterns that might indicate exploitation attempts, while security teams should consider implementing web filtering solutions that can detect and block potentially malicious CSS mask-image operations. This vulnerability aligns with CWE-200 (Information Exposure) and represents a variant of credential leakage attacks that fall under ATT&CK technique T1552 (Credentials in Files) and T1552.001 (Credentials in Files - Credentials In Files). The remediation process should also include user education about avoiding untrusted websites and maintaining current software versions, as this vulnerability demonstrates the importance of keeping browser components updated to address subtle but critical security flaws in web rendering engines.