CVE-2007-4478 in Internet Explorer
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Microsoft Internet Explorer 6.0 and 7 allows user-assisted remote attackers to inject arbitrary web script or HTML in the local zone via a URI, when the document at the associated URL is saved to a local file, which then contains the URI string along with the document s original content.
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Analysis
by VulDB Data Team • 04/07/2017
This cross-site scripting vulnerability exists in Microsoft Internet Explorer versions 6.0 and 7, representing a significant security flaw that enables remote attackers to execute malicious code through user-assisted exploitation. The vulnerability specifically targets the local zone security context where documents are saved to local files, creating a dangerous attack vector that leverages the browser's handling of URI strings within saved content. The flaw occurs when a document containing a malicious URI is saved locally, causing the URI string to be embedded within the document's content alongside the original material. This creates a persistent XSS condition that can be triggered when the saved document is subsequently opened in the vulnerable browser version.
The technical mechanism of this vulnerability stems from Internet Explorer's inadequate sanitization of URI strings when processing documents saved to the local zone. When a user visits a malicious website and saves a document containing a crafted URI, the browser fails to properly escape or filter the URI components before embedding them within the local file's content. This allows attackers to inject arbitrary HTML and script code that executes when the saved document is opened, effectively bypassing the browser's security restrictions for local zone content. The vulnerability is classified as a user-assisted attack because the victim must first visit the malicious website and save the compromised document, making it more difficult to exploit automatically but still highly dangerous in targeted scenarios.
The operational impact of this vulnerability extends beyond simple script injection to potentially enable full system compromise through a series of chained attacks. When malicious code executes within the local zone context, it can leverage the browser's permissions to access local resources, modify files, or even download additional malware components. Attackers can craft payloads that exploit the saved document's local execution context to perform actions such as reading local files, modifying system settings, or establishing persistence mechanisms. The vulnerability aligns with CWE-79 which describes cross-site scripting flaws, and represents a specific instance of how local file handling can create security boundaries that are easily circumvented. This type of attack vector is particularly concerning in enterprise environments where users may inadvertently save compromised documents from untrusted sources.
Mitigation strategies for this vulnerability require a multi-layered approach combining browser updates, user education, and administrative controls. Microsoft addressed this issue through security updates that improved URI sanitization in the local zone handling process, though the vulnerability remained exploitable in older versions. Organizations should implement strict policies regarding document handling from untrusted sources, particularly when dealing with saved content from web browsers. Network-level protections such as web application firewalls and content filtering solutions can help detect and block malicious URI patterns before they reach users. The ATT&CK framework categorizes this vulnerability under T1059 for command and scripting interpreters, as the injected scripts can execute shell commands and manipulate system resources. Additionally, browser hardening measures including disabling local file access and implementing strict security zones can significantly reduce the attack surface for this specific vulnerability class.