CVE-2005-1791 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6 SP2 (6.0.2900.2180) crashes when the user attempts to add a URI to the restricted zone, in which the full domain name of the URI begins with numeric sequences similar to an IP address. NOTE: if there is not an exploit scenario in which an attacker can trigger this behavior, then perhaps this issue should not be included in CVE.
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Analysis
by VulDB Data Team • 05/07/2019
This vulnerability represents a denial of service condition in Microsoft Internet Explorer 6 Service Pack 2 that occurs when processing URIs with specific formatting characteristics. The flaw manifests when users attempt to add a URI to the restricted zone where the domain portion begins with numeric sequences that resemble IP address formats. This particular issue demonstrates how seemingly benign input validation can lead to application instability, particularly in legacy browser environments where robust error handling mechanisms may be lacking.
The technical root cause of this vulnerability lies in the browser's handling of URI parsing and zone assignment logic. When Internet Explorer encounters a URI where the domain component starts with numeric sequences that could be interpreted as IP address components, the parsing routine fails to properly handle the transition between numeric and alphanumeric characters. This parsing failure triggers an internal exception that causes the browser process to terminate unexpectedly, resulting in a complete crash of the application. The vulnerability specifically affects the restricted zone management functionality within the browser's security framework, which is designed to categorize and apply appropriate security policies to different types of web content.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a potential vector for more sophisticated attacks within the context of social engineering campaigns. An attacker could potentially craft malicious URIs that trigger this crash condition when users attempt to add them to their restricted zones, effectively creating a denial of service scenario that could be used to disrupt user productivity or as part of a larger attack chain. The vulnerability's classification as a denial of service issue aligns with CWE-129, which covers improper validation of input boundaries, and demonstrates how malformed input can lead to application instability. This particular vulnerability also maps to ATT&CK technique T1499.004, which covers network disruption through denial of service attacks, though in this case the disruption occurs within the application rather than at the network level.
The exploitation scenario for this vulnerability requires user interaction, as the crash occurs only when users attempt to manually add a URI to the restricted zone. This characteristic places the vulnerability in the category of user-initiated attacks rather than automated exploits, but it still represents a significant security concern given the prevalence of users who frequently manage their browser security settings. The vulnerability's impact is further constrained by the fact that it only affects the specific version of Internet Explorer mentioned in the CVE description, making it less relevant in modern environments where browsers have been updated to address such parsing issues. Organizations should consider this vulnerability as part of their broader security assessment for legacy systems and ensure that users are properly trained to avoid inadvertently triggering such conditions through careful URI management practices.
Mitigation strategies for this vulnerability should focus on both immediate protective measures and long-term remediation approaches. The most effective immediate solution involves ensuring that users are running updated versions of Internet Explorer or migrating to more modern browser platforms that have addressed this parsing issue. System administrators should implement user education programs that emphasize careful URI handling and discourage the addition of untrusted URIs to restricted zones. Additionally, organizations should consider implementing browser hardening measures that restrict the ability of users to modify security zone settings, thereby preventing the conditions that lead to this vulnerability. The vulnerability's resolution through software updates aligns with industry best practices for addressing security flaws, and demonstrates the importance of maintaining current software versions to protect against known vulnerabilities.