Advisory details:
pypa / pyload-ng/PYSEC-2026-496
| Advisory ID | pypa/pyload-ng/PYSEC-2026-496 |
| Aliases |
CVE-2025-53890
GHSA-8w3f-4r8f-pf53 PYSEC-2026-496 |
| Summary | pyLoad vulnerable to XSS through insecure CAPTCHA #### Summary An unsafe JavaScript evaluation vulnerability in pyLoad’s CAPTCHA processing code allows **unauthenticated remote attackers** to execute **arbitrary code** in the client browser and potentially the backend server. Exploitation requires no user interaction or authentication and can result in session hijacking, credential theft, and full system rce. #### Details The vulnerable code resides in ```javascript function onCaptchaResult(result) { eval(result); // Direct execution of attacker-controlled input } ``` * The `onCaptchaResult()` function directly passes CAPTCHA results (sent from the user) into `eval()` * No sanitization or validation is performed on this input * A malicious CAPTCHA result can include JavaScript such as `fetch()` or `child_process.exec()` in environments using NodeJS * Attackers can fully hijack sessions and pivot to remote code execution on the server if the environment allows it ### Reproduction Methods 1. **Official Source Installation**: ```bash git clone https://github.com/pyload/pyload cd pyload git checkout 0.4.20 python -m pip install -e . pyload --userdir=/tmp/pyload ``` 2. **Virtual Environment**: ```bash python -m venv pyload-env source pyload-env/bin/activate pip install pyload==0.4.20 pyload ``` ## CAPTCHA Endpoint Verification **Technical Clarification**: 1. The vulnerable endpoint is actually: ``` /interactive/captcha ``` 2. Complete PoC Request: ```http POST /interactive/captcha HTTP/1.1 Host: localhost:8000 Content-Type: application/x-www-form-urlencoded cid=123&response=1%3Balert(document.cookie) ``` 3. Curl Command Correction: ```bash curl -X POST "http://localhost:8000/interactive/captcha" \ -d "cid=123&response=1%3Balert(document.cookie)" ``` 1. **Vulnerable Code Location**: The eval() vulnerability is confirmed in: ``` src/pyload/webui/app/static/js/captcha-interactive.user.js ``` ### **Resources** 1. https://github.com/pyload/pyload/commit/909e5c97885237530d1264cfceb5555870eb9546 2. [OWASP: Avoid `eval()`](https://cheatsheetseries.owasp.org/cheatsheets/JavaScript_Security_Cheat_Sheet.html#eval) 3. [#4586](https://github.com/pyload/pyload/pull/4586) |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 8.8 |
| Risk | 4.4 |
| 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 |
|---|---|---|
| cvssv3.1 | 9.8 | https://github.com/pypa/advisory-database/blob/main/vulns/pyload-ng/PYSEC-2026-496.yaml |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/pyload/pyload | ||
| https://github.com/pyload/pyload/commit/909e5c97885237530d1264cfceb5555870eb9546 | ||
| https://github.com/pyload/pyload/pull/4586 | ||
| https://pypi.org/project/pyload-ng | ||
| CVE-2025-53890 | https://nvd.nist.gov/vuln/detail/CVE-2025-53890 | |
| GHSA-8w3f-4r8f-pf53 | https://github.com/advisories/GHSA-8w3f-4r8f-pf53 | |
| GHSA-8w3f-4r8f-pf53 | https://github.com/pyload/pyload/security/advisories/GHSA-8w3f-4r8f-pf53 |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
Vector: SSVCv2/E:P/A:Y/T:T/P:M/B:A/M:M/D:R/2025-07-15T13:24:23Z/
Decision: Track*
Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2025/53xxx/CVE-2025-53890.json
Source Advisory: vulnrichment/CVE-2025-53890
[{'Exploitation': 'poc'},
{'Automatable': 'yes'},
{'Technical Impact': 'total'},
{'Mission Prevalence': 'minimal'},
{'Public Well-being Impact': 'material'},
{'Mission & Well-being': 'medium'}]