CVE-2026-42221

8.1 HIGH 1% exploit odds Fix listed Auth & access Server

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.
Exploit odds: 1.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-05-04 21:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-10-26 19:10 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 1.3% in the next 30 days (EPSS).
Severity: 8.1 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-05-04 21:16 UTC
Last modified: 2026-10-26 19:10 UTC
Exploit probability: 1.3% · EPSS, next 30 days
Weakness: CWE-306 · Missing authentication
Record status: Analyzed

Affected

Nginxui nginx Ui < 2.3.8

Attack profile CVSS 3.1 · 8.1

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

Is it in your code?

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Fix and advisories

References

NVD record · CVE.org record