CVE-1999-0793 is a vulnerability in Microsoft Internet Explorer versions 4.0.1 and 5.0 that allows remote attackers to read local files by redirecting data to a JavaScript applet. This vulnerability arises from improper handling of data streams within the browser, enabling an attacker to craft a malicious web page that exploits the browser's capability to redirect data to JavaScript applets. By doing so, the attacker can access and read files on the victim's local system without authorization. The vulnerability does not require user authentication but does require the victim to visit a malicious or compromised website hosting the exploit. The CVSS score of 2.6 (low severity) reflects the limited impact and the higher attack complexity, as the attacker must lure the user to a malicious site and the exploit depends on older browser versions that are no longer widely used. The vulnerability impacts confidentiality by allowing unauthorized reading of local files but does not affect integrity or availability. Microsoft released patches to address this issue, as documented in security bulletin MS99-043. No known exploits have been reported in the wild, likely due to the age of the affected software and the availability of patches.

For European organizations, the direct impact of this vulnerability today is minimal due to the obsolescence of Internet Explorer versions 4.0.1 and 5.0. Modern browsers have replaced these versions, and most organizations have migrated to supported software. However, legacy systems or specialized environments that still run these outdated browsers could be at risk. In such cases, an attacker could potentially read sensitive local files, leading to information disclosure. This could include configuration files, credentials stored in accessible locations, or other sensitive data. The confidentiality breach could facilitate further attacks or data leaks. Given the low CVSS score and absence of known exploits, the threat is not critical but should be addressed in environments where legacy software remains in use. European organizations with strict data protection regulations (e.g., GDPR) must ensure that legacy systems do not expose sensitive personal or corporate data through such vulnerabilities.

Organizations should verify that no systems are running Internet Explorer versions 4.0.1 or 5.0. If such systems exist, immediate remediation steps include applying the official Microsoft patch MS99-043 or upgrading to a supported and secure browser version. Network-level controls can be implemented to block access to untrusted or malicious websites that could host exploit code. Additionally, organizations should conduct audits to identify legacy software usage and plan for decommissioning or upgrading outdated systems. Employing endpoint protection solutions that monitor and block suspicious script execution can provide an additional layer of defense. User education to avoid visiting untrusted websites is also recommended, particularly in environments where legacy browsers cannot be immediately replaced.