CVE-2015-5826 in iOS
Summary
by MITRE
WebKit in Apple iOS before 9 does not properly select the cases in which a Cascading Style Sheets (CSS) document is required to have the text/css content type, which allows remote attackers to bypass the Same Origin Policy via a crafted web site.
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Analysis
by VulDB Data Team • 11/22/2024
The vulnerability identified as CVE-2015-5826 resides within Apple iOS versions prior to 9.0, specifically affecting the WebKit rendering engine that powers Safari and other web-based applications on the platform. This flaw represents a critical security oversight in how the browser handles CSS document content type validation, creating a pathway for malicious actors to exploit the same origin policy mechanism that is fundamental to web security. The issue stems from improper handling of CSS content type detection, allowing attackers to craft web pages that manipulate how browsers interpret CSS resources.
The technical implementation of this vulnerability involves WebKit's failure to properly validate the text/css content type when processing CSS documents. When a web page loads CSS resources, browsers typically enforce strict content type checking to ensure that resources are properly formatted and to prevent cross-site scripting attacks. However, in affected iOS versions, WebKit would incorrectly process CSS documents that did not explicitly declare the text/css content type, leading to a bypass of the same origin policy restrictions. This misconfiguration allows malicious websites to load CSS content from different origins without proper security checks, effectively undermining the browser's security model.
The operational impact of this vulnerability extends beyond simple policy bypass, as it enables sophisticated attack vectors that can lead to data theft, session hijacking, and cross-site request forgery. Attackers can leverage this weakness to construct malicious web pages that load CSS resources from third-party domains, potentially accessing sensitive information or performing unauthorized actions on behalf of users. The vulnerability is particularly dangerous because it operates at the core rendering engine level, making it difficult to detect and prevent through traditional web application firewalls or security measures. This flaw aligns with CWE-200, which addresses information exposure through improper error handling, and represents a significant deviation from secure coding practices that should enforce strict content type validation.
Mitigation strategies for this vulnerability require immediate system updates to iOS 9.0 or later, where Apple implemented proper content type validation for CSS documents. Organizations should also implement network-level protections such as content security policies that restrict CSS loading from untrusted sources, and deploy web application firewalls that can detect and block suspicious CSS content patterns. Additionally, security teams should conduct thorough penetration testing to identify any web applications that may be vulnerable to this specific attack vector, ensuring that all user-facing web interfaces properly validate content types and enforce strict cross-origin resource sharing policies. The ATT&CK framework categorizes this vulnerability under T1059 for command and scripting interpreter, as attackers can leverage the bypassed security controls to execute malicious code through crafted web content.