CVE-2012-2899 in Chrome
Summary
by MITRE
Google Chrome before 21.0.1180.82 on iOS makes certain incorrect calls to WebView methods that trigger use of an applewebdata: URL, which allows remote attackers to bypass the Same Origin Policy and conduct Universal XSS (UXSS) attacks via vectors involving the document.write method.
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Analysis
by VulDB Data Team • 05/06/2018
The vulnerability identified as CVE-2012-2899 represents a critical security flaw in Google Chrome versions prior to 21.0.1180.82 on iOS platforms. This issue stems from improper handling of WebView method calls that inadvertently trigger the use of applewebdata: URLs, creating a significant bypass of Chrome's fundamental security mechanisms. The vulnerability specifically affects the Same Origin Policy implementation, which serves as a cornerstone of web security by preventing unauthorized access to resources across different origins. When Chrome incorrectly processes these WebView calls, it enables attackers to circumvent the policy enforcement that typically protects against cross-site scripting attacks.
The technical exploitation of this vulnerability occurs through the document.write method, which allows attackers to inject malicious content into web pages. This particular method, when combined with the improper handling of applewebdata: URLs, creates a pathway for Universal XSS attacks that can target any website visited by the user. The applewebdata: URL scheme is a special protocol used by iOS Safari and Chrome to access internal web content, but when misused through incorrect WebView method calls, it provides attackers with elevated privileges within the browser's security context. This flaw operates at the intersection of web browser security architecture and mobile platform integration, leveraging the unique characteristics of iOS web rendering.
The operational impact of CVE-2012-2899 extends beyond typical XSS vulnerabilities due to its Universal XSS nature, meaning it can affect any website regardless of its security measures or the user's browsing context. Attackers can craft malicious payloads that exploit this flaw to steal session cookies, perform unauthorized actions on behalf of users, or redirect them to phishing sites. The vulnerability is particularly dangerous because it operates within the browser's core rendering engine and can bypass traditional security controls that would normally prevent such attacks. This makes it a prime target for sophisticated attack campaigns that seek to exploit user trust in legitimate websites while maintaining persistent access to sensitive data.
From a cybersecurity perspective, this vulnerability aligns with CWE-94, which describes the weakness of "Improper Control of Generation of Code" and relates to CWE-352, addressing "Cross-Site Request Forgery," though the primary classification involves improper handling of web resource access. The attack vector follows patterns consistent with ATT&CK technique T1059.001 for command and scripting interpreter and T1211 for exploitation for defense bypass. Mitigation strategies should focus on immediate patch deployment for all affected Chrome versions, implementation of Content Security Policy headers, and browser security hardening measures. Organizations should also consider implementing additional monitoring for suspicious document.write operations and establishing incident response procedures for potential exploitation of this vulnerability. The fix required for this issue involved correcting the WebView method call handling to properly enforce the Same Origin Policy and prevent unauthorized access to applewebdata: URL schemes.