# CVE-1999-0537: Microsoft Internet Explorer and Netscape Navigator insecure active content execution

Source: https://junglewise.ai/threats/cve-1999-0537-microsoft-internet-explorer-and-netscape-navigator-insecure-active  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 1998-04-01. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-1999-0537 · Severity: high · CVSS 7.5 · Published 1998-04-01

A configuration issue in early web browsers like Internet Explorer and Netscape Navigator allows the automatic execution of active content such as ActiveX, Java, and JavaScript. This could allow malicious websites to run unauthorized code on a user's computer, potentially leading to data theft or system compromise. Organizations should ensure that browser security settings are configured to restrict or prompt for the execution of untrusted active content.

Technologies: [Microsoft Internet Explorer](https://junglewise.ai/threats/technologies/internet-explorer), [Netscape Navigator](https://junglewise.ai/threats/technologies/navigator). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft), [Netscape](https://junglewise.ai/threats/vendors/netscape).

## Quick answers

**Is CVE-1999-0537 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-1999-0537 being exploited in the wild.

**How severe is CVE-1999-0537?** High severity, with a CVSS score of 7.5, published 1 April 1998.

**Which products and versions are affected?** Microsoft Internet Explorer; Netscape Netscape Navigator.

**Is there a fix for CVE-1999-0537?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-1999-0537 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-1999-0537?** Check whether you run Microsoft Internet Explorer, Netscape Communicator or Netscape Navigator. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

This vulnerability stems from insecure default configurations or user-defined settings in legacy web browsers that permit the automatic execution of active content. By hosting malicious ActiveX controls, Java applets, or JavaScript on a webpage, an attacker can achieve remote code execution or unauthorized data access when a user visits the site. The attack vector is network-based and requires no prior authentication, relying on the browser's failure to sandbox or restrict these technologies effectively. Modern mitigations involve disabling legacy technologies like ActiveX and implementing strict Content Security Policies (CSP).

## Affected products

- Microsoft Internet Explorer
- Netscape Netscape Navigator

## Timeline

- 1998-04-01: disclosed

## References

- [https://www.cve.org/CVERecord?id=CVE-1999-0537](https://www.cve.org/CVERecord?id=CVE-1999-0537)

## Related threats

- [Microsoft Internet Explorer use-after-free privilege escalation](https://junglewise.ai/threats/cve-2026-83741-use-after-free-in-internet-explorer-allows-an-authorized-attacker)
- [Microsoft Internet Explorer use-after-free in HTML object handling](https://junglewise.ai/threats/cve-2010-0249-microsoft-internet-explorer-use-after-free-in-html-object-handling)
- [Microsoft Internet Explorer use-after-free in Peer Objects](https://junglewise.ai/threats/cve-2010-0806-microsoft-internet-explorer-use-after-free-in-peer-objects)
- [Microsoft Internet Explorer use-after-free in CSS processing](https://junglewise.ai/threats/cve-2010-3962-microsoft-internet-explorer-use-after-free-in-css-processing)
- [Microsoft Internet Explorer use after free in mshtml.dll](https://junglewise.ai/threats/cve-2013-3893-microsoft-internet-explorer-use-after-free-in-mshtml-dll)