#VU21781 Input validation error in PyYAML - CVE-2017-18342

Vulnerability identifier: #VU21781

Vulnerability risk: High

CVSSv4.0: 7.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2017-18342

CWE-ID: CWE-20

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 execute arbitrary code.

The vulnerability exists due to insufficient validation of user-supplied input in the "yaml.load()" API (yaml.safe_load is not used). A remote attacker can execute arbitrary code on the target system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

PyYAML: 3.01 - 3.13

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External links
https://github.com/yaml/pyyaml/blob/master/CHANGES
https://github.com/yaml/pyyaml/pull/74

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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.