cve/2021/CVE-2021-3640.md

### [CVE-2021-3640](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3640)
![](https://img.shields.io/static/v1?label=Product&message=kernel&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=%3D%20Affects%20kernel%20v5.15.3%20and%20prior%2C%20Fixed%20in%20v5.16-rc1%20and%20above.%20&color=brighgreen)
![](https://img.shields.io/static/v1?label=Vulnerability&message=CWE-362%20-%20Concurrent%20Execution%20using%20Shared%20Resource%20with%20Improper%20Synchronization%20('Race%20Condition')%2C%20CWE-416%20-%20Use%20After%20Free.&color=brighgreen)

### Description

A flaw use-after-free in function sco_sock_sendmsg() of the Linux kernel HCI subsystem was found in the way user calls ioct UFFDIO_REGISTER or other way triggers race condition of the call sco_conn_del() together with the call sco_sock_sendmsg() with the expected controllable faulting memory page. A privileged local user could use this flaw to crash the system or escalate their privileges on the system.

### POC

#### Reference
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/bluetooth/sco.c?h=v5.16&id=99c23da0eed4fd20cae8243f2b51e10e66aa0951
- https://ubuntu.com/security/CVE-2021-3640
- https://www.openwall.com/lists/oss-security/2021/07/22/1

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