cve/2021/CVE-2021-43843.md

### [CVE-2021-43843](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-43843)
![](https://img.shields.io/static/v1?label=Product&message=jsx-slack&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=%3C%204.5.2%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=CWE-1333%3A%20Inefficient%20Regular%20Expression%20Complexity&color=brightgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=CWE-400%3A%20Uncontrolled%20Resource%20Consumption&color=brightgreen)

### Description

jsx-slack is a package for building JSON objects for Slack block kit surfaces from JSX. The maintainers found the patch for CVE-2021-43838 in jsx-slack v4.5.1 is insufficient tfor protection from a Regular Expression Denial of Service (ReDoS) attack. If an attacker can put a lot of JSX elements into `<blockquote>` tag _with including multibyte characters_, an internal regular expression for escaping characters may consume an excessive amount of computing resources. v4.5.1 passes the test against ASCII characters but misses the case of multibyte characters. jsx-slack v4.5.2 has updated regular expressions for escaping blockquote characters to prevent catastrophic backtracking. It is also including an updated test case to confirm rendering multiple tags in `<blockquote>` with multibyte characters.

### POC

#### Reference
No PoCs from references.

#### Github
- https://github.com/ARPSyndicate/cvemon
- https://github.com/ChamalBandara/CVEs