CVE-2026-42221 Details
Nginx UI is a web user interface for the Nginx web server. From version 2.0.0 to before version 2.3.8, an unauthenticated network attacker can claim the initial administrator account on a fresh nginx-ui instance during the first-run setup window. The public /api/install endpoint is reachable without authentication, and the request-encryption flow only protects payload confidentiality in transit; it does not authenticate who is allowed to perform installation. A remote attacker who reaches the service before the legitimate operator can set the admin email, username, and password, causing permanent initial-instance takeover. This issue has been patched in version 2.3.8.
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Exploit prediction scoring system (EPSS) score for CVE-2026-42221
EPSS (Exploit Prediction Scoring System): EPSS predicts the likelihood that a vulnerability will be exploited in the wild. A higher percentage means a greater chance of an exploit occurring. The EPSS model produces a probability score between 0 and 1 (0 and 100%).
0.35 Probability of exploitation activity being observed over the next 30 days (26th percentile)
CVSS score for CVE-2026-42221
CVSS (Common Vulnerability Scoring System): An open framework owned and managed by FIRST.Org, Inc. that assigns a numerical score from 0 to 10 to software vulnerabilities to indicate their severity.
8.1 High
Products affected by CVE-2026-42221
Nginx Ui 2.0.0
Nginx Ui 2.2.0
Nginx Ui 2.1.4
DVE Score by Bitsight AI
DVE scores complement traditional static scoring systems like CVSS with Bitsight AI powered real-time threat intelligence and underground cyber criminal activity so that security teams can reduce alert fatigue and focus on vulnerabilities most likely to be exploited.
Low
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CVE-2026-42221 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
CN 103 24.64%
US 76 18.18%
SG 33 7.89%
DE 32 7.66%
RU 31 7.42%
FR 16 3.83%
TH 13 3.11%
HK 12 2.87%
VN 11 2.63%
KR 8 1.91%

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CVE-2026-42221 Industry Footprint

Top 10 Identified Industries

*Service provider organizations (typically Technology and Telecommunications) are disproportionally represented in the results given their upstream ownership of end-user infrastructure. See our FAQs.

Industry* Observations Percentage
Technology 247 87.90%
Telecommunications 29 10.32%
Finance 1 0.36%
Education 1 0.36%
Retail 1 0.36%
Transportation 1 0.36%
Engineering 1 0.36%

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