CVE-2019-20477

Name: CVE-2019-20477
Creator: NVD / NIST
Published: 2020-02-19T04:15:10.803+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 5.03%

Last modified Jun 17, 2026

CVE-2019-20477 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. PyYAML 5.1 through 5.1.2 has insufficient restrictions on the load and load_all functions because of a class deserialization issue, e.g., Popen is a class in the subprocess module. NOTE: this issue exists because of an incomplete fix for CVE-2017-18342.. EPSS estimates a 5.03% chance of exploitation in the next 30 days.

Description

PyYAML 5.1 through 5.1.2 has insufficient restrictions on the load and load_all functions because of a class deserialization issue, e.g., Popen is a class in the subprocess module. NOTE: this issue exists because of an incomplete fix for CVE-2017-18342.

Metrics

CVSS 3.1

9.8/10

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

EPSS Probability

5.03%

91.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-502

Affected Software

Vendor	Product	Versions
Pyyaml	Pyyaml	>= 5.1, <= 5.1.2
Fedoraproject	Fedora	30
Fedoraproject	Fedora	31

References

https://github.com/yaml/pyyaml/blob/master/CHANGESRelease Notes, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/33VBUY73AA6CTTYL3LRWHNFDULV7PFPN/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/52N5XS73Z5S4ZN7I7R56ICCPCTKCUV4H/
https://www.exploit-db.com/download/47655Exploit, Third Party Advisory, VDB Entry
https://github.com/yaml/pyyaml/blob/master/CHANGESRelease Notes, Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/33VBUY73AA6CTTYL3LRWHNFDULV7PFPN/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/52N5XS73Z5S4ZN7I7R56ICCPCTKCUV4H/
https://www.exploit-db.com/download/47655Exploit, Third Party Advisory, VDB Entry

Timeline

Published: Feb 19, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2019-20477?

How severe is CVE-2019-20477?

CVE-2019-20477 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 5.03% probability of exploitation in the next 30 days.

How do I fix CVE-2019-20477?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2019-20477?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST