VulnerabilityPublished 6 May 2026

CVE-2026-42238: Nginx-UI is Vulnerable to Unauthenticated Remote Code Execution via Backup Restore

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

Authoritative record:CVE-2026-42238· Critical 9.0

Not known to be exploited · CVSS 9.0 Critical : upgrade to 2.3.8 as a priority.

Data as of 27 Oct 2026, 00:07 UTC

CVSS 4.0 base score

9.0Critical

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

Patch: Available – fixed in 2.3.8

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: Passive
Vulnerable system confidentiality: High
Vulnerable system integrity: High
Vulnerable system availability: High
Subsequent system confidentiality: High
Subsequent system integrity: High
Subsequent system availability: High

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

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: Passive: Successful exploitation of this vulnerability requires limited interaction by the targeted user with the vulnerable system and the attacker’s payload. These interactions would be considered involuntary and do not require that the user actively subvert protections built into the vulnerable system.
Vulnerable system confidentiality: High: There is a total loss of confidentiality, resulting in all information within the Vulnerable System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Vulnerable system 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 vulnerable system. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the vulnerable system.
Vulnerable system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Vulnerable System; 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 Vulnerable System (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).
Subsequent system confidentiality: High: There is a total loss of confidentiality, resulting in all resources within the Subsequent System being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact. For example, an attacker steals the administrator's password, or private encryption keys of a web server.
Subsequent system 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 Subsequent System. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the Subsequent System.
Subsequent system availability: High: There is a total loss of availability, resulting in the attacker being able to fully deny access to resources in the Subsequent System; 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 Subsequent System (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 v4.0 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

Upgrade github.com/0xJacky/nginx-ui to 2.3.8.

Affected software

Product	Affected	Fixed in
Gogithub.com/0xJacky/nginx-ui	Affected <2.3.8	Fixed in 2.3.8

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

**Product:** nginx-ui **Repository:** `0xJacky/nginx-ui` (branch: `dev`) **Vulnerability Class:** Authentication Bypass → Arbitrary File Write → OS Command Injection **Affected Component:** `POST /api/restore` --- ## 1. Vulnerability Summary nginx-ui exposes a backup restore endpoint (`POST /api/restore`) that is **completely unauthenticated** during the first 10 minutes after process startup on any fresh installation. An unauthenticated remote attacker can upload a crafted backup archive that overwrites the application's configuration file (`app.ini`) and SQLite database. Because the attacker controls the restored `app.ini`, they can inject an arbitrary OS command into the `TestConfigCmd` setting. After the application automatically restarts to apply the restored config, a single follow-up request triggers that command as the user running nginx-ui — typically `root` in Docker deployments. The 10-minute unauthenticated window resets on every process restart, making this exploitable not only on initial deployments but on any restart event (container restart, upgrade, health-check-triggered restart). --- ## 2. Root Cause Analysis ### 2.1 The Restore Route Is Registered Without Authentication `backup.InitRouter` is called on the `root` group, which carries only `IPWhiteList()` middleware — no `AuthRequired()`: [1](#2-0) The route definition: [2](#2-1) ### 2.2 The `authIfInstalled` Guard Has a Time-Bounded Bypass The only authentication guard on the restore route is `authIfInstalled`: [3](#2-2) It calls `AuthRequired()` only when `InstallLockStatus() || IsInstallTimeoutExceeded()` is true. Both conditions are false on a fresh install within the first 10 minutes: [4](#2-3) - `InstallLockStatus()` returns `false` because `JwtSecret` is `""` on a fresh install and `SkipInstallation` defaults to `false`. - `IsInstallTimeoutExceeded()` returns `false` for the first 10 minutes after `startupTime` is set in `init()`. When both are `false`, `authIfInstalled` calls `ctx.Next()` with **zero authentication**. ### 2.3 The `EncryptedForm` Middleware Is Not a Security Barrier The `EncryptedForm()` middleware between `authIfInstalled` and `RestoreBackup` is **optional** — it only activates if the request includes an `encrypted_params` field. If that field is absent, it calls `c.Next()` immediately: [5](#2-4) An attacker sends a plain `multipart/form-data` request without `encrypted_params` and the middleware is a no-op. ### 2.4 The Attacker Controls the AES Key Used to Verify the Backup The restore handler accepts the AES key and IV directly from the attacker via the `security_token` form field: [6](#2-5) The manifest integrity check derives its HMAC signing key **from the attacker-supplied AES key**: [7](#2-6) Since the attacker crafts the backup and supplies the key, they can produce a valid HMAC signature for any manifest content they choose. The integrity check is self-referential and provides no security against a crafted backup. ### 2.5 Restore Overwrites `app.ini` and the SQLite Database Unconditionally When `restore_nginx_ui=true`, `restoreNginxUIConfig` directly copies files from the backup onto disk with no content validation: [8](#2-7) ### 2.6 Restored `TestConfigCmd` Is Executed as a Shell Command After restore, `risefront.Restart()` is called, reloading `app.ini`: [9](#2-8) On the next call to `TestConfig()`, the value of `TestConfigCmd` from the restored `app.ini` is passed verbatim to `/bin/sh -c`: [10](#2-9) [11](#2-10) --- ## 3. Attack Prerequisites | Requirement | Notes | |---|---| | Network access to nginx-ui port | Default: 9000/tcp | | Target is a fresh install | `JwtSecret` is empty in `app.ini` | | Within 10 minutes of last process start | Window resets on every restart | | IP not blocked by `IPWhiteList` | Default config has no IP whitelist | The 10-minute window is not a meaningful mitigation in practice. Docker containers restart frequently due to health checks, upgrades, and orchestrator rescheduling. Any restart resets `startupTime` via `init()`, reopening the window. --- ## 4. Step-by-Step Proof of Concept ### Step 1 — Confirm the installation window is open ```http GET /api/install HTTP/1.1 Host: target:9000 ``` Expected response confirming vulnerability: ```json {"lock": false, "timeout": false} ``` ### Step 2 — Craft the malicious backup The backup format (derived from `internal/backup/backup.go`) is: ``` backup-TIMESTAMP.zip ← outer ZIP (unencrypted) ├── manifest.json ← JSON manifest ├── manifest.sig ← HMAC-SHA256 of manifest.json ├── nginx-ui.zip ← AES-CBC encrypted inner ZIP └── nginx.zip ← AES-CBC encrypted inner ZIP ``` **2a.** Generate a random 32-byte AES key and 16-byte IV. **2b.** Create the malicious `app.ini` to place inside `nginx-ui.zip`: ```ini [app] JwtSecret = attacker_chosen_jwt_secret_32chars [node] Secret = attacker_chosen_node_secret [nginx] TestConfigCmd = cur

CWE-94Improper Control of Generation of Code ('Code Injection') (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #10OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.
Architecture and Design · Refactoring
Refactor your program so that you do not have to dynamically generate code.
Architecture and Design
Run your code in a "jail" or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which code can be executed by your product.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V5.2.8 (opens in a new tab)
V5.2.5 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
Leverage Executable Code in Non-Executable Files (opens in a new tab)
Manipulating User-Controlled Variables (opens in a new tab)
Code Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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Affected software

Description

WeaknessesCWE-94

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