PYSEC-2020-96: pyyaml fixed in 5.3.1

PYSEC-2020-96 PUBLISHED CVSS 9.300000190734863 CRITICAL

Record from OSV · Published March 24, 2020

pyyaml is fixed in 5.3.1 (PyPI)

A vulnerability was discovered in the PyYAML library in versions before 5.3.1, 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. An attacker could use this flaw to execute arbitrary code on the system by abusing the python/object/new constructor.

Fixed versions

Upgrade to a fixed version or later. Language registries are listed first, then Linux distributions, then vendor products.

Package	Ecosystem	Fixed in
pyyaml	PyPI	5.3.1

Risk scores

CVSS 4.0

9.300000190734863

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

Affected products

Vendor	Product	Versions
PyPI	pyyaml	5.1, 5.1, 5.1.1

Timeline

Mar 24, 2020 CVE Published
May 4, 2026 CVE Updated

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