Use-after-free in Linux kernel fsconfig

1) Use-after-free

EUVDB-ID: #VU59840

Risk: Low

CVSSv3.1: 7.9 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:P/RL:O/RC:C]

CVE-ID: CVE-2021-4154

CWE-ID: CWE-416 - Use After Free

Exploit availability: Yes

Description

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to a use-after-free error within the cgroup1_parse_param() function in kernel/cgroup/cgroup-v1.c in Linux kernel's cgroup v1 parser. A local user can execute arbitrary code via the fsconfig syscall parameter leading to a container breakout.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

Linux kernel: before 5.14 rc2

External links

http://bugzilla.redhat.com/show_bug.cgi?id=2034514

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.