#VU25542 Improper access control in PyYAML - CVE-2019-20477

Vulnerability identifier: #VU25542

Vulnerability risk: High

CVSSv4.0: 8.1 [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:U/U:Amber]

CVE-ID: CVE-2019-20477

CWE-ID: CWE-284

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
PyYAML
Web applications / Modules and components for CMS

Vendor: The YAML Project

Description

The vulnerability allows a remote attacker to gain unauthorized access to otherwise restricted functionality.

The vulnerability exists due to improper access restrictions in the "load" and "load_all" functions. A remote attacker can bypass implemented security restrictions and gain unauthorized access to the application.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

PyYAML: 5.1

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External links
https://github.com/yaml/pyyaml/blob/master/CHANGES
https://www.exploit-db.com/download/47655
https://github.com/yaml/pyyaml/issues/265

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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.