CVE-1999-0490 in Internet Explorer
Summary
by MITRE
MSHTML.DLL in Internet Explorer 5.0 allows a remote attacker to learn information about a local user's files via an IMG SRC tag.
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Analysis
by VulDB Data Team • 04/19/2026
This vulnerability exists in the MSHTML.DLL component of Internet Explorer 5.0 and represents a classic information disclosure flaw that leverages the browser's handling of image source attributes. The vulnerability specifically manifests when processing an IMG SRC tag that references local file paths, allowing remote attackers to potentially enumerate or access local file system information. This type of vulnerability falls under the category of path traversal and information disclosure attacks that were prevalent during the late 1990s web browser era. The flaw exploits how Internet Explorer's HTML rendering engine processes local file references within image tags, creating an unintended information leak mechanism.
The technical implementation of this vulnerability occurs through the MSHTML.DLL's parsing and rendering behavior when encountering malformed or specially crafted IMG SRC attributes. When a remote attacker crafts an IMG tag with a local file path reference, the browser's rendering engine may inadvertently expose file system information or provide indicators about the existence of specific files or directories on the victim's system. This behavior stems from insufficient input validation and proper boundary checking within the HTML parsing routines. The vulnerability is particularly concerning because it allows attackers to perform reconnaissance activities without direct system access, potentially gathering intelligence about local file structures, user directories, or system configurations through simple web page requests.
Operationally, this vulnerability creates significant security implications for users of Internet Explorer 5.0, as it enables remote attackers to perform passive reconnaissance against target systems. The impact extends beyond simple information gathering, as attackers could use this technique to map local file systems, identify sensitive files, or discover system configurations that could aid in subsequent attacks. The vulnerability is classified under CWE-200 (Information Exposure) and represents a precursor to more sophisticated path traversal attacks that would later become common in web applications. This type of attack vector aligns with ATT&CK technique T1083 (File and Directory Discovery) and demonstrates how browser-based vulnerabilities can enable lateral movement and reconnaissance activities.
The mitigation strategies for this vulnerability primarily involve updating to patched versions of Internet Explorer, as Microsoft released security updates specifically addressing this issue. Users should also implement proper network segmentation and firewall rules to limit access to internal file systems, though this approach has limitations given the nature of web-based attacks. Browser security configurations should be reviewed to disable unnecessary local file access capabilities, and users should be educated about the risks of visiting untrusted websites. Additionally, implementing web application firewalls and content filtering systems can help detect and block malicious IMG SRC tags that attempt to access local resources. Organizations should also consider deploying network monitoring solutions to detect unusual patterns of local file system enumeration attempts that might indicate exploitation of this vulnerability. The vulnerability serves as an important historical example of how seemingly benign HTML parsing operations can create security risks when proper input validation is not implemented.