cve/2021/CVE-2021-33503.md

### [CVE-2021-33503](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-33503)
![](https://img.shields.io/static/v1?label=Product&message=n%2Fa&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=n%2Fa&color=blue)
![](https://img.shields.io/static/v1?label=Vulnerability&message=n%2Fa&color=brighgreen)

### Description

An issue was discovered in urllib3 before 1.26.5. When provided with a URL containing many @ characters in the authority component, the authority regular expression exhibits catastrophic backtracking, causing a denial of service if a URL were passed as a parameter or redirected to via an HTTP redirect.

### POC

#### Reference
- https://www.oracle.com/security-alerts/cpuoct2021.html

#### Github
- https://github.com/HotDB-Community/HotDB-Engine
- https://github.com/dbrennand/virustotal-python
- https://github.com/engn33r/awesome-redos-security
- https://github.com/fkie-cad/nvd-json-data-feeds
- https://github.com/p-rog/cve-analyser