### [CVE-2021-29984](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29984)
![](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%2078.13%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Version&message=%3C%2091%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=Incorrect%20instruction%20reordering%20during%20JIT%20optimization&color=brighgreen)

### Description

Instruction reordering resulted in a sequence of instructions that would cause an object to be incorrectly considered during garbage collection. This led to memory corruption and a potentially exploitable crash. This vulnerability affects Thunderbird < 78.13, Thunderbird < 91, Firefox ESR < 78.13, and Firefox < 91.

### POC

#### Reference
No PoCs from references.

#### Github
- https://github.com/googleprojectzero/fuzzilli
- https://github.com/zhangjiahui-buaa/MasterThesis