CVE-1999-0790 is a vulnerability identified in Netscape Communicator version 4.0, a legacy web browser product. The vulnerability allows a remote attacker to read information from the user's cache through JavaScript code executed in the browser. Specifically, this means that malicious JavaScript embedded in a web page could access cached content stored by the browser, potentially exposing sensitive information such as previously visited web pages, cached credentials, or other cached data. The attack vector is remote and does not require authentication, but the attack complexity is high due to the need to bypass browser security models and the limited capabilities of JavaScript at the time. The vulnerability impacts confidentiality only, with no effect on integrity or availability. The CVSS score is 2.6 (low severity), reflecting the limited impact and difficulty of exploitation. No patches are available, and there are no known exploits in the wild. Given the age of the product and the obsolescence of Netscape Communicator 4.0, this vulnerability is primarily of historical interest but could still pose risks in legacy environments where this browser is in use.

For European organizations, the practical impact of this vulnerability today is minimal due to the obsolescence of Netscape Communicator 4.0. However, in rare cases where legacy systems or specialized environments still use this browser, sensitive cached information could be exposed to remote attackers via malicious web content. This could lead to information disclosure, potentially compromising user privacy or revealing internal browsing history. The vulnerability does not allow modification or disruption of data or services, limiting its impact to confidentiality breaches. Given the low CVSS score and lack of known exploits, the threat level is low, but organizations with legacy systems should be aware of the risk. Modern browsers have long since addressed similar issues with stricter same-origin policies and sandboxing, so the impact is negligible for most European enterprises using current technology.

Since no official patches are available for this vulnerability, the most effective mitigation is to discontinue use of Netscape Communicator 4.0 entirely. Organizations should migrate users and systems to modern, supported browsers that implement robust security controls against cache and script-based attacks. For environments where legacy systems must be maintained, network-level controls such as web filtering to block malicious JavaScript content, strict content security policies, and isolation of legacy systems from sensitive networks can reduce exposure. Additionally, educating users about the risks of visiting untrusted websites and disabling JavaScript where feasible on legacy browsers can help mitigate exploitation. Regular security audits to identify and phase out outdated software are recommended to prevent similar risks.