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 public /api/install endpoint without authentication. This leads to permanent takeover of the initial instance by setting the admin email, username, and password. The vulnerability arises because the installation endpoint lacks authentication, and encryption only protects data in transit, not the authorization of the installer. This issue has been fixed in version 2.3.
AI Analysis
Technical Summary
The vulnerability in nginx-ui (CVE-2026-42221) involves missing authentication for a critical function: the initial installation setup. Versions from 2.0.0 to before 2.3.8 expose the /api/install endpoint publicly without requiring authentication. An attacker who accesses this endpoint before the legitimate operator during the first-run setup can set administrator credentials, effectively taking over the instance permanently. The encryption used only protects the confidentiality of the payload during transmission but does not authenticate the installer. The vendor addressed this issue 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 unauthenticated installation endpoint. This compromises confidentiality, integrity, and availability of the affected system. The attacker can set arbitrary admin credentials, resulting in permanent initial-instance takeover. There are no known exploits in the wild as of the published date.
Mitigation Recommendations
This vulnerability is patched in nginx-ui version 2.3.8. Users should upgrade to version 2.3.8 or later to remediate this issue. Since no official patch link or advisory is provided, verify the upgrade availability from the vendor's official sources. Until patched, restrict network access to the installation endpoint to trusted users only to reduce exposure.
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 public /api/install endpoint without authentication. This leads to permanent takeover of the initial instance by setting the admin email, username, and password. The vulnerability arises because the installation endpoint lacks authentication, and encryption only protects data in transit, not the authorization of the installer. This issue has been fixed in version 2.3.
CVSS v3.1
Score 8.1high
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in nginx-ui (CVE-2026-42221) involves missing authentication for a critical function: the initial installation setup. Versions from 2.0.0 to before 2.3.8 expose the /api/install endpoint publicly without requiring authentication. An attacker who accesses this endpoint before the legitimate operator during the first-run setup can set administrator credentials, effectively taking over the instance permanently. The encryption used only protects the confidentiality of the payload during transmission but does not authenticate the installer. The vendor addressed this issue 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 unauthenticated installation endpoint. This compromises confidentiality, integrity, and availability of the affected system. The attacker can set arbitrary admin credentials, resulting in permanent initial-instance takeover. There are no known exploits in the wild as of the published date.
Mitigation Recommendations
This vulnerability is patched in nginx-ui version 2.3.8. Users should upgrade to version 2.3.8 or later to remediate this issue. Since no official patch link or advisory is provided, verify the upgrade availability from the vendor's official sources. Until patched, restrict network access to the installation endpoint to trusted users only to reduce exposure.
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: 5/12/2026, 6:24:56 AM
Last updated: 6/18/2026, 6:46:47 PM
Views: 80
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