CVE-2010-0051 in Safari
Summary
by MITRE
WebKit in Apple Safari before 4.0.5 does not properly validate the cross-origin loading of stylesheets, which allows remote attackers to obtain sensitive information via a crafted HTML document. NOTE: this might overlap CVE-2010-0651.
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Analysis
by VulDB Data Team • 05/02/2026
The vulnerability described in CVE-2010-0051 represents a critical cross-origin resource sharing flaw within Apple Safari's WebKit rendering engine prior to version 4.0.5. This issue stems from inadequate validation mechanisms that govern how web browsers handle stylesheet loading across different origins, creating a potential information disclosure channel that adversaries could exploit to gain unauthorized access to sensitive data. The vulnerability specifically affects the browser's security model for handling cross-origin requests, particularly when processing stylesheet resources from external domains.
The technical flaw manifests in the WebKit engine's failure to properly enforce same-origin policies when processing CSS resources loaded from remote servers. When Safari encounters a stylesheet request from a different origin, the browser should validate that the resource can be safely loaded and that no sensitive information is exposed through the loading process. However, the implementation contained a gap that allowed attackers to craft malicious HTML documents that could trigger unintended behavior in the browser's stylesheet loading mechanism, potentially revealing information about the underlying system or user sessions.
This vulnerability operates at the intersection of several security principles and can be categorized under CWE-200, Information Exposure, and CWE-345, Insufficient Verification of Data Authenticity. The operational impact of this flaw extends beyond simple information disclosure, as it represents a fundamental breakdown in the browser's security architecture that could enable more sophisticated attacks. Attackers could potentially leverage this vulnerability to gather information about user sessions, system configurations, or other sensitive data that should remain protected by cross-origin restrictions. The threat landscape for this vulnerability aligns with ATT&CK technique T1071.001 for Application Layer Protocol: Web Protocols, where adversaries exploit weaknesses in web browser implementations to gain unauthorized access to information.
The security implications of CVE-2010-0051 are particularly concerning given Safari's widespread use and the fact that this vulnerability existed in versions that were commonly deployed in enterprise and consumer environments. The flaw demonstrates how seemingly minor implementation gaps in browser security can create significant risks, especially when considering that stylesheet loading is a common web interaction that occurs frequently during normal browsing activities. Users who encountered malicious web pages containing crafted HTML documents could unknowingly expose sensitive information to remote attackers without any visible indication of compromise.
Mitigation strategies for this vulnerability required immediate patching of Safari installations to version 4.0.5 or later, which addressed the cross-origin stylesheet validation issue. Organizations should have implemented comprehensive browser update policies to ensure all systems were protected against this vulnerability. Additionally, network administrators could have employed web filtering solutions to block access to known malicious domains that might exploit this vulnerability, though such measures would not address the core issue within the browser itself. The vulnerability also highlighted the importance of regular security assessments of browser components and the need for continuous monitoring of security advisories from vendors like Apple. Security teams should have prioritized this vulnerability in their risk assessment frameworks due to its potential for information disclosure and the widespread use of affected Safari versions in both corporate and personal environments.