#VU51627 Use of insufficiently random values in cloud-init (Ubuntu package) - CVE-2020-8631

Vulnerability identifier: #VU51627

Vulnerability risk: Low

CVSSv4.0: 0.4 [CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2020-8631

CWE-ID: CWE-330

Exploitation vector: Local

Exploit availability: No

Vulnerable software:
cloud-init (Ubuntu package)
Operating systems & Components / Operating system package or component

Vendor: Canonical Ltd.

Description

The vulnerability allows a local user to predict passwords.

The vulnerability exists due to cloud-init relies on Mersenne Twister for a random password, which uses the random.choice() function in rand_str() in cloudinit/util.py. A local user can guess randomly generated passwords and gain unauthorized access.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

cloud-init (Ubuntu package): 0.5.0 - 19.4

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External links
https://lists.opensuse.org/opensuse-security-announce/2020-03/msg00042.html
https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/1860795
https://github.com/canonical/cloud-init/pull/204
https://lists.debian.org/debian-lts-announce/2020/02/msg00021.html

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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.