Input validation error in PyYAML - CVE-2020-14343
Published: July 4, 2021 / Updated: November 28, 2025
Vulnerability identifier: #VU54520
CSH Severity: High
CVSS v4.0: 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
Exploitation vector: Remote access
Exploit availability:
Public exploit is available
Vendor: The YAML Project
Affected software:
PyYAML
PyYAML
Detailed vulnerability 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.
How to mitigate CVE-2020-14343
Install updates from vendor's website.