CVEs-PoC/2021/CVE-2021-23960.md

### [CVE-2021-23960](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-23960)
![](https://img.shields.io/static/v1?label=Product&message=Firefox%20ESR&color=blue)
![](https://img.shields.io/static/v1?label=Product&message=Firefox&color=blue)
![](https://img.shields.io/static/v1?label=Product&message=Thunderbird&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=%3C%2078.7%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Version&message=%3C%2085%20&color=brightgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=Use-after-poison%20for%20incorrectly%20redeclared%20JavaScript%20variables%20during%20GC&color=brightgreen)

### Description

Performing garbage collection on re-declared JavaScript variables resulted in a user-after-poison, and a potentially exploitable crash. This vulnerability affects Firefox < 85, Thunderbird < 78.7, and Firefox ESR < 78.7.

### POC

#### Reference
- https://bugzilla.mozilla.org/show_bug.cgi?id=1675755

#### Github
No PoCs found on GitHub currently.