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Vulnerability record · CVE-2020-14343 · published 9 February 2021

CVE-2020-14343: Pyyaml improper input validation vulnerability

Pyyaml · Pyyaml

A vulnerability was discovered in the PyYAML library in versions before 5.4, where it is susceptible to arbitrary code execution when it processes untrusted YAML files through the full_load method or with the FullLoader loader. Applications that use the library to process untrusted input may be vulnerable to this flaw. This flaw allows an attacker to execute arbitrary code on the system by abusing the python/object/new constructor. This flaw is due to an incomplete fix for CVE-2020-1747.

9.8 CVSS 3.1 Critical EPSS 6.0% · top 6.9% CWE-20 · Improper input validation
9.8CVSS 3.1 base score, v2 10.0
6.0%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
10References
17 Jun 2026Last modified by NVD

Description

A vulnerability was discovered in the PyYAML library in versions before 5.4, where it is susceptible to arbitrary code execution when it processes untrusted YAML files through the full_load method or with the FullLoader loader. Applications that use the library to process untrusted input may be vulnerable to this flaw. This flaw allows an attacker to execute arbitrary code on the system by abusing the python/object/new constructor. This flaw is due to an incomplete fix for CVE-2020-1747.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.redhat.com/show_bug.cgi?id=1860466 Issue TrackingThird Party Advisory
https://github.com/SeldonIO/seldon-core/issues/2252
https://github.com/yaml/pyyaml/issues/420
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1860466 Issue TrackingThird Party Advisory
https://github.com/SeldonIO/seldon-core/issues/2252
https://github.com/yaml/pyyaml/issues/420
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2020-14343), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.