PT-2026-36921 · Nginx-Ui · Nginx-Ui

R1Zzg0D · Published 2026-04-21 · Updated 2026-05-11 · CVE-2026-42221

Positive Technologies (AI Summary)

CVSS v3.1

9.8

Critical

Base vector

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

Name of the Vulnerable Software and Affected Versions Nginx UI versions 2.0.0 through 2.3.7

Description An unauthenticated network attacker can claim the initial administrator account on a fresh instance during the first-run setup window. The public endpoint "/api/install" is accessible without authentication. While the request-encryption flow ensures payload confidentiality during transit, it fails to authenticate the user performing the installation. A remote attacker who accesses the service before the legitimate operator can define the admin email, username, and password, leading to a permanent takeover of the initial instance.

Recommendations Update to version 2.3.8.

Exploit

Fix

Missing Authentication

Weakness Enumeration

CWE-306

Related Identifiers

BDU:2026-06343

CVE-2026-42221

GHSA-H27V-PH7W-M9FP

Affected Products

Nginx-Ui

References · 12

• 🔥 https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-h27v-ph7w-m9fp · Exploit
• https://nvd.nist.gov/vuln/detail/CVE-2026-42221 · Security Note
• https://osv.dev/vulnerability/GHSA-h27v-ph7w-m9fp · Vendor Advisory
• https://bdu.fstec.ru/vul/2026-06343 · Security Note
• https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.8 · Note
• https://github.com/0xJacky/nginx-ui · Note
• https://twitter.com/VulmonFeeds/status/2051480452003741951 · Twitter Post
• https://twitter.com/integ_sec/status/2053848485993050217 · Twitter Post
• https://t.me/cveNotify/162089 · Telegram Post
• https://t.me/CVEtracker/52677 · Telegram Post
• https://twitter.com/CVEnew/status/2051403817548206572 · Twitter Post
• https://twitter.com/infoflowcloud/status/2051405546842927540 · Twitter Post