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CVE-2019-20477

32
FAUCET Score

CVE-2019-20477 is a critical deserialization vulnerability in PyYAML versions 5.1 through 5.1.2, affecting products like Fedora and PyYAML itself. This flaw, an incomplete fix for a previous CVE, allows for arbitrary code execution due to insufficient restrictions on the load and load_all functions. With a CVSS score of 9.8, it presents a critical risk, allowing unauthenticated attackers to achieve full compromise (confidentiality, integrity, and availability) with low attack complexity over the network. Despite its severity, there is currently no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 5.1, <= 5.1.2CPE matchmatch criteria
cpe:2.3:a:pyyaml:pyyaml:*:*:*:*:*:*:*:*
30CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
31CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
5.16%
Probability of exploitation in next 30 days
EPSS Percentile
91.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0516 is in the 86th percentile among its peer group of 36,833 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (15)

pippatch availablevia ghsa
Product: pyyamlFixed in: 5.2
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: python38:3.8-8030020200818121840.4190259b
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/clair-rhel8:v3.4.0-25
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-bridge-operator-bundle:v3.4.0-3
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-bridge-operator-rhel8:v3.4.0-17
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-builder-qemu-rhcos-rhel8:v3.4.0-17
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-builder-rhel8:v3.4.0-18
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-container-security-operator-bundle:v3.4.0-2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-container-security-operator-rhel8:v3.4.0-2
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-openshift-bridge-rhel8-operator:v3.4.0-17
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-operator-bundle:v3.4.0-89
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-operator-rhel8:v3.4.0-132
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Quay 3Fixed in: quay/quay-rhel8:v3.4.0-51
View patch
redhatend of lifevia redhat_api
Product: Red Hat OpenStack Platform 10 (Newton)Fixed in: PyYAML
redhatend of lifevia redhat_api
Product: Red Hat OpenStack Platform 13 (Queens)Fixed in: PyYAML

Vendor Advisories (2)

pipGHSA-3pqx-4fqf-j49fcritical

Deserialization of Untrusted Data in PyYAML

Apr 20, 2021
redhatCVE-2019-20477Moderate

PyYAML: command execution through python/object/apply constructor in FullLoader

Nov 18, 2019

References

github.com / yaml/pyyaml/blob/master/CHANGES
Release NotesThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/33VBUY73AA6CTTYL3LRWHNFDULV7PFPN
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/52N5XS73Z5S4ZN7I7R56ICCPCTKCUV4H
exploit-db.com / download/47655
ExploitThird Party AdvisoryVDB Entry