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CVE-1999-1591

23
FAUCET Score

CVE-1999-1591 describes an authentication bypass vulnerability in Microsoft Internet Information Services (IIS) 4.0 SP4, specifically when certain hotfixes are not applied. This flaw allows remote attackers to bypass authentication requirements, as demonstrated by connections made via Microsoft Visual InterDev 6.0. With a CVSS score of 7.5 (HIGH), this vulnerability is easily exploitable over the network with low attack complexity, potentially leading to partial compromise of confidentiality, integrity, and availability. Despite its age and severity, there is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
4.0CPE matchmatch criteria
cpe:2.3:a:microsoft:internet_information_server:4.0:sp4:*:*:*:*:*:*
6.0CPE matchmatch criteria
cpe:2.3:a:microsoft:visual_interdev:6.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

7.5HIGH

AV:N/AC:L/Au:N/C:P/I:P/A:P

Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
PARTIAL
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Exploitability Score
10.0
Impact Score
6.4
CvssVersion
2.0

Exploit Intelligence

EPSS Score
11.27%
Probability of exploitation in next 30 days
EPSS Percentile
95.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.1127 is in the 93rd percentile among its peer group of 51,485 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

archives.neohapsis.com / archives/ntbugtraq/1998-1999/msg00276.html
archives.neohapsis.com / archives/ntbugtraq/1998-1999/msg00277.html
securityfocus.com / bid/190