CVE-2026-33028: Github.com/0xJacky/Nginx UI Nginx-ui Has Race Condition That Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-m468-xcm6-fxg4",
  "modified" : "2026-03-30T21:25:51Z",
  "published" : "2026-03-30T16:34:35Z",
  "aliases" : [ "CVE-2026-33028" ],
  "summary" : "nginx-ui has Race Condition that Leads to Persistent Data Corruption and Service Collapse",
  "details" : "### Summary\nThe `nginx-ui` application is vulnerable to a **Race Condition**. Due to the complete absence of synchronization mechanisms (Mutex) and non-atomic file writes, concurrent requests lead to the severe corruption of the primary configuration file (`app.ini`). This vulnerability results in a persistent Denial of Service (DoS) and introduces a non-deterministic path for **Remote Code Execution (RCE)** through configuration cross-contamination.\n\n### Details\nThe vulnerability exists because the settings update pipeline does not implement any synchronization primitives. When multiple requests reach the handler simultaneously:\n1.  **Memory Corruption**: `ProtectedFill()` modifies shared global singleton pointers without thread-safety, leading to inconsistent states in memory.\n2.  **File Corruption**: The underlying library (`gopkg.in/ini.v1`) performs direct overwrites. Concurrent write operations interleave at the OS level, resulting in `app.ini` files with empty leading lines, truncated fields, or partially overwritten configuration keys.\n3.  **State Persistent Failure**: Depending on which bytes are corrupted, the application either fails its \"is-installed\" check (redirecting to `/install`) or encounters a fatal error during boot/runtime that prevents the process from responding to any further requests.\n\n**Environment:**\n- **OS**: Kali Linux 6.17.10-1kali1 (6.17.10+kali-amd64)\n- **Application Version**: nginx-ui v2.3.3 (513) e5da6dd (go1.26.0)\n- **Deployment**: Docker Container\n\n### PoC\n0. Check original app.ini file valid state:\n<img width=\"524\" height=\"367\" alt=\"image\" src=\"https://github.com/user-attachments/assets/d9688f76-7fe7-46ea-9eb9-c55bf40918a6\" />\n\n1. Log in to the `nginx-ui` dashboard.\n2. Navigate to Preferences and update settings. Capture a `POST /api/settings` request and send it to **Burp Suite Intruder**.\n3. Configure the attack with **Null payloads** (to test basic concurrency) or a **Fuzzing list** (to test data-driven corruption).\n4. Set the **Resource Pool** to 20-50 concurrent requests.\n<img width=\"1188\" height=\"776\" alt=\"image\" src=\"https://github.com/user-attachments/assets/403eef43-2bc6-4651-8802-15ddcb4f7631\" />\n\n5. **Observation (In-flight corruption)**: Monitor the `app.ini` file. You will observe the file being written with empty leading lines or incomplete key-value pairs. \n\n- <img width=\"1316\" height=\"390\" alt=\"image\" src=\"https://github.com/user-attachments/assets/d99553f7-d253-4525-9b45-f59994e69180\" />\n------------------------------------------------\n\n- <img width=\"1368\" height=\"709\" alt=\"image\" src=\"https://github.com/user-attachments/assets/7522ba29-39f1-4c22-88f2-8e859cdb1984\" />\n\n6. **Observation (Recovery Failure)**: If the service redirects to `/install`, attempting to complete the setup again often fails because the underlying configuration state is too corrupted to be reconciled by the installer logic.\n7. **Observation (Total Service Collapse)**: When the corruption in `app.ini` becomes so severe, the Go runtime or the INI parser encounters a fatal error, causing the Nginx-UI service to stop responding entirely (Hard DoS).\n\n<img width=\"1344\" height=\"542\" alt=\"image\" src=\"https://github.com/user-attachments/assets/da4b99dc-ddce-4b79-b0bb-2d634bdd3bf7\" />\n\n8. **Observation (Cross-Section Contamination)**: During testing, it was observed that sometimes INI sections become interleaved. For example, fields belonging to the `[nginx]` section (like `ConfigDir` or `ReloadCmd`) were erroneously written under the `[webauthn]` section.\n   \n   **Example of corrupted output observed:**\n```\n[webauthn]\nRPDisplayName  = \nRPID           = \nRPOrigins      = \ngDirWhiteList  = \nConfigDir      = /etc/nginx\nConfigPath     = \nPIDPath        = /run/nginx.pid\nSbinPath       = \nTestConfigCmd  = \nReloadCmd      = nginx -s reload\nRestartCmd     = nginx -s stop\nStubStatusPort = 51820\nContainerName  = \n```\n\n### Impact\nThis is a **High** security risk (CWE-362: Race Condition).\n- **Integrity**: Permanent corruption of application settings and system-level configuration.\n- **Availability**: High. The attack results in a persistent Denial of Service that cannot be recovered via the web UI.\n- **Remote Code Execution (RCE)** Risk: Since the application allows updating certain fields (like Node Name) and uses others as shell commands (like ReloadCmd or RestartCmd), the observed \"cross-contamination\" of INI values means an attacker could potentially force a user-controlled string into a command execution field. If ReloadCmd is overwritten with a malicious payload provided in another field, the next nginx reload will execute that payload. While highly impactful, this specific exploit path is non-deterministic and depends on the precise interleaving of thread execution, making targeted exploitation difficult.\n\n### Recommended Mitigation\n1.  **Implement Mutex Locking**: Wrap the `ProtectedFill` and `settings.Save()` calls in a `sync.Mutex` to serialize access to global settings.\n2.  **Atomic File Writes**: Implement a \"write-then-rename\" strategy. Write the new configuration to `app.ini.tmp` and use `os.Rename()` to replace the original file atomically, ensuring the configuration file is always in a valid state.\n\nA patched version of nginx-ui  is available at https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.4.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/0xJacky/Nginx-UI"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "1.99"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/uozi-tech/cosy"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.30.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.30.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-m468-xcm6-fxg4"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33028"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/0xJacky/nginx-ui"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.4"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-362" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-30T16:34:35Z",
    "nvd_published_at" : "2026-03-30T18:16:18Z"
  }
}