Remote code execution in PyYAML for Python

1) Input validation error

EUVDB-ID: #VU54520

Risk: High

CVSSv4.0: 8.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Amber]

CVE-ID: CVE-2020-14343

CWE-ID: CWE-20 - Improper input validation

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to insufficient validation of user-supplied input when processing untrusted YAML files through the full_load method or with the FullLoader loader. A remote attacker can pass specially crafted input to the application and execute arbitrary code on the system by abusing the python/object/new constructor.

Note, the vulnerability exists due to incomplete patch for vulnerability #VU25823.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

PyYAML: 5.1 - 5.3.1

CPE2.3

• cpe:2.3:a:the_yaml_project:pyyaml:5.1:*:*:*:*:python:*:*
• cpe:2.3:a:the_yaml_project:pyyaml:5.1.1:*:*:*:*:python:*:*
• cpe:2.3:a:the_yaml_project:pyyaml:5.1.2:*:*:*:*:python:*:*

External links

https://bugzilla.redhat.com/show_bug.cgi?id=1860466

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.