CVE catalog

CVE-2019-20477

pyyaml: CVE-2019-20477

Severity: Critical · CVSS 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: Feb 19, 2020, 4:15:00 AM UTC
Source: [NVD] · [CVE record]
EPSS: 5.11% · Oct 22, 2026

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.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	pyyaml	sid	`6.0.3-1`	fixed
Debian	pyyaml	forky	`6.0.3-1`	fixed
Debian	pyyaml	trixie	`6.0.2-1`	fixed
Debian	pyyaml	bookworm	`6.0-3`	fixed

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	pyyaml	source	sid	`5.2-1`	unimportant	Not reported	Not reported
Debian	pyyaml	source	forky	`5.2-1`	unimportant	Not reported	Not reported
Debian	pyyaml	source	trixie	`5.2-1`	unimportant	Not reported	Not reported
Debian	pyyaml	source	bookworm	`5.2-1`	unimportant	Not reported	Not reported

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[python3-yaml]Fixed
Source package: [pyyaml]
Details (2)
- 6.0-3+b2 · amd64 · bookworm
  Fixed · Fixed: 5.2-1
  dsa · pyyaml · debian · bookworm; dsa · pyyaml · debian · 12
- 6.0-3+b2 · arm64 · bookworm
  Fixed · Fixed: 5.2-1
  dsa · pyyaml · debian · bookworm; dsa · pyyaml · debian · 12

[Debian 13 (Trixie)]

[python3-yaml]Fixed
Source package: [pyyaml]
Details (2)
- 6.0.2-1+b2 · amd64 · trixie
  Fixed · Fixed: 5.2-1
  dsa · pyyaml · debian · 13
- 6.0.2-1+b2 · arm64 · trixie
  Fixed · Fixed: 5.2-1
  dsa · pyyaml · debian · 13

Observed: Oct 23, 2026, 5:43:48 PM UTC

References

[Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX]