How severe is CVE-1999-1233?

CVE-1999-1233 has a CVSS 2.0 base score of 7.5, rated high severity.

Is CVE-1999-1233 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-1999-1233?

CVE-1999-1233 affects Microsoft Internet Information Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-1999-1233?

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-1999-1233 published?

CVE-1999-1233 was published on 1999-12-31 and last updated on 2026-06-16.

CVE-1999-1233

CVE-1999-1233 is a high-severity vulnerability in Microsoft Internet Information Server 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

Severity: High (CVSS 2.0 base score 7.5)
EPSS exploit prediction: 5% (92nd percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microsoft Internet Information Server
Published: 1999-12-31
Last modified: 2026-06-16

Description

IIS 4.0 does not properly restrict access for the initial session request from a user's IP address if the address does not resolve to a DNS domain, aka the "Domain Resolution" vulnerability.

Frequently asked questions

What is CVE-1999-1233?: IIS 4.0 does not properly restrict access for the initial session request from a user's IP address if the address does not resolve to a DNS domain, aka the "Domain Resolution" vulnerability.
How severe is CVE-1999-1233?: CVE-1999-1233 has a CVSS 2.0 base score of 7.5, rated high severity.
Is CVE-1999-1233 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 5% (92nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-1999-1233?: CVE-1999-1233 affects Microsoft Internet Information Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-1999-1233?: 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-1999-1233 published?: CVE-1999-1233 was published on 1999-12-31 and last updated on 2026-06-16.

References

Affected products (1)

cpe:2.3:a:microsoft:internet_information_server:4.0:*:*:*:*:*:*:*

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