CVE-1999-1087

CVE-1999-1087 is a high-severity vulnerability in Microsoft Internet Explorer with a CVSS 2.0 base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Description

Internet Explorer 4 treats a 32-bit number ("dotless IP address") in the a URL as the hostname instead of an IP address, which causes IE to apply Local Intranet Zone settings to the resulting web page, allowing remote malicious web servers to conduct unauthorized activities by using URLs that contain the dotless IP address for their server.

Frequently asked questions

What is CVE-1999-1087?
Internet Explorer 4 treats a 32-bit number ("dotless IP address") in the a URL as the hostname instead of an IP address, which causes IE to apply Local Intranet Zone settings to the resulting web page, allowing remote malicious web servers to conduct unauthorized activities by using URLs that contain the dotless IP address for their server.
How severe is CVE-1999-1087?
CVE-1999-1087 has a CVSS 2.0 base score of 7.5, rated high severity.
Is CVE-1999-1087 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 6% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-1999-1087?
CVE-1999-1087 primarily affects Microsoft Internet Explorer. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-1999-1087?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-1999-1087 published?
CVE-1999-1087 was published on 1999-12-31 and last updated on 2026-06-16.

References

Affected products (3)

More vulnerabilities in Microsoft Internet Explorer

All CVEs affecting Microsoft Internet Explorer →