cve/2021/CVE-2021-3996.md

### [CVE-2021-3996](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3996)
![](https://img.shields.io/static/v1?label=Product&message=util-linux&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=n%2Fa&color=blue)
![](https://img.shields.io/static/v1?label=Vulnerability&message=CWE-552%20-%20Files%20or%20Directories%20Accessible%20to%20External%20Parties&color=brighgreen)

### Description

A logic error was found in the libmount library of util-linux in the function that allows an unprivileged user to unmount a FUSE filesystem. This flaw allows a local user on a vulnerable system to unmount other users' filesystems that are either world-writable themselves (like /tmp) or mounted in a world-writable directory. An attacker may use this flaw to cause a denial of service to applications that use the affected filesystems.

### POC

#### Reference
- http://packetstormsecurity.com/files/170176/snap-confine-must_mkdir_and_open_with_perms-Race-Condition.html

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