CVE-2026-42221: CWE-306: Missing Authentication for Critical Function in 0xJacky nginx-ui
CVE-2026-42221 is a high-severity vulnerability in 0xJacky's nginx-ui versions 2. 0. 0 up to but not including 2. 3. 8. It allows an unauthenticated remote attacker to claim the initial administrator account during the first-run setup by accessing the publicly available /api/install endpoint. The vulnerability arises because this endpoint does not require authentication and the encryption only protects data confidentiality, not authentication. Exploitation results in permanent takeover of the initial admin account. This issue has been fixed in version 2. 3.
AI Analysis
Technical Summary
The vulnerability CVE-2026-42221 affects nginx-ui, a web user interface for the Nginx web server, in versions from 2.0.0 to before 2.3.8. During the initial setup phase, the /api/install endpoint is exposed without authentication, allowing an unauthenticated attacker to set the administrator email, username, and password before the legitimate operator does. This leads to a permanent takeover of the initial admin account. The flaw is classified as CWE-306 (Missing Authentication for Critical Function). The vulnerability has been patched in version 2.3.8.
Potential Impact
An unauthenticated remote attacker can gain full administrative control over a fresh nginx-ui instance by exploiting the exposed /api/install endpoint during the initial setup window. This compromises confidentiality, integrity, and availability of the affected system, as the attacker can permanently control the admin account. There are no known exploits in the wild as of the published date.
Mitigation Recommendations
Upgrade nginx-ui to version 2.3.8 or later, where this vulnerability is patched. Since the issue is fixed in this version, no additional mitigation steps are required for patched instances. For unpatched instances, restrict network access to the initial setup interface until the upgrade can be applied.
CVE-2026-42221: CWE-306: Missing Authentication for Critical Function in 0xJacky nginx-ui
Description
CVE-2026-42221 is a high-severity vulnerability in 0xJacky's nginx-ui versions 2. 0. 0 up to but not including 2. 3. 8. It allows an unauthenticated remote attacker to claim the initial administrator account during the first-run setup by accessing the publicly available /api/install endpoint. The vulnerability arises because this endpoint does not require authentication and the encryption only protects data confidentiality, not authentication. Exploitation results in permanent takeover of the initial admin account. This issue has been fixed in version 2. 3.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability CVE-2026-42221 affects nginx-ui, a web user interface for the Nginx web server, in versions from 2.0.0 to before 2.3.8. During the initial setup phase, the /api/install endpoint is exposed without authentication, allowing an unauthenticated attacker to set the administrator email, username, and password before the legitimate operator does. This leads to a permanent takeover of the initial admin account. The flaw is classified as CWE-306 (Missing Authentication for Critical Function). The vulnerability has been patched in version 2.3.8.
Potential Impact
An unauthenticated remote attacker can gain full administrative control over a fresh nginx-ui instance by exploiting the exposed /api/install endpoint during the initial setup window. This compromises confidentiality, integrity, and availability of the affected system, as the attacker can permanently control the admin account. There are no known exploits in the wild as of the published date.
Mitigation Recommendations
Upgrade nginx-ui to version 2.3.8 or later, where this vulnerability is patched. Since the issue is fixed in this version, no additional mitigation steps are required for patched instances. For unpatched instances, restrict network access to the initial setup interface until the upgrade can be applied.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-25T05:04:37.029Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69f90348cbff5d8610482e3a
Added to database: 5/4/2026, 8:36:24 PM
Last enriched: 5/4/2026, 8:51:30 PM
Last updated: 5/4/2026, 9:38:07 PM
Views: 3
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