CVE-2012-1872 in Internet Explorer
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Microsoft Internet Explorer 6 through 9 allows remote attackers to inject arbitrary web script or HTML via crafted character sequences with EUC-JP encoding, aka "EUC-JP Character Encoding Vulnerability."
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Analysis
by VulDB Data Team • 01/21/2025
The CVE-2012-1872 vulnerability represents a critical cross-site scripting flaw in Microsoft Internet Explorer versions 6 through 9, specifically exploiting the browser's handling of EUC-JP character encoding. This vulnerability falls under the CWE-79 category of Cross-Site Scripting, which is a fundamental web application security weakness that allows attackers to inject malicious scripts into web pages viewed by other users. The flaw occurs when Internet Explorer encounters crafted character sequences encoded in EUC-JP format, which is a multi-byte character encoding standard primarily used for Japanese text. The vulnerability stems from the browser's inadequate validation and sanitization of EUC-JP encoded data during the rendering process, creating an opportunity for attackers to bypass security mechanisms that typically protect against XSS attacks.
The technical exploitation of this vulnerability involves attackers crafting malicious web content that uses EUC-JP encoding to deliver XSS payloads. When Internet Explorer processes these character sequences, the browser's parser fails to properly handle the encoding, allowing malicious scripts to be executed within the context of the victim's browser session. This creates a persistent threat vector where attackers can inject HTML content, JavaScript code, or other malicious payloads that execute automatically when users view affected web pages. The vulnerability is particularly dangerous because it leverages the browser's native character encoding handling rather than relying on other attack vectors, making it more difficult to detect and prevent through traditional security measures.
The operational impact of CVE-2012-1872 extends beyond simple script execution, as it can enable sophisticated attack chains that compromise user sessions and data integrity. Attackers can leverage this vulnerability to steal session cookies, perform unauthorized actions on behalf of users, redirect victims to malicious sites, or harvest sensitive information from web applications. The vulnerability affects a broad range of Internet Explorer versions, making it particularly dangerous in enterprise environments where legacy browser support is common. Organizations running vulnerable systems face significant risks including data breaches, credential theft, and potential lateral movement within network environments, as the compromised browser sessions can provide attackers with access to internal resources and applications that are typically protected by network security controls.
Mitigation strategies for this vulnerability require a multi-layered approach combining immediate patching, browser configuration changes, and network-level protections. Microsoft released security updates that addressed the character encoding handling in affected Internet Explorer versions, and organizations should prioritize applying these patches to eliminate the vulnerability. Browser security settings can be adjusted to disable active content processing for untrusted sites, while web application firewalls and content security policies can help detect and block malicious EUC-JP encoded content. Additionally, implementing proper input validation and output encoding in web applications can provide defense-in-depth against similar vulnerabilities. The ATT&CK framework categorizes this vulnerability under the T1059.007 technique for "Scripting - JavaScript" and T1566.001 for "Phishing - Spearphishing Attachment", highlighting the need for comprehensive security measures that address both the technical flaw and the attack patterns that exploit it. Organizations should also consider migrating away from legacy browser versions to more secure modern alternatives that have better security implementations and ongoing support.