CVE-2019-20477

Exp

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.

Published: 2020-02-19 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2019-20477 is rated High Exploit Risk (75.8/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 0.42%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2019-20477

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2019-20477

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-22 0.47% 0.42% -0.05%
2 2026-03-21 0.43% 0.47% +0.03%
3 2026-01-14 — 0.43% —

Full EPSS history (20 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2019-20477

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2019-20477

GitHub Security Advisory for CVE-2019-20477

GHSA-3pqx-4fqf-j49f · Severity: critical · Ecosystem: pip — Deserialization of Untrusted Data in PyYAML

OS Trackers for CVE-2019-20477

vendor priority summary link
debian unimportant CVE-2019-20477 unimportant priority: Debian including 1 source packages (pyyaml), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2019-20477
redhat medium — https://access.redhat.com/security/cve/CVE-2019-20477
ubuntu low CVE-2019-20477 low priority: Ubuntu including 1 source packages (pyyaml), 6 status rows across 6 suites (bionic, eoan, focal, trusty, upstream, xenial): not-affected 4, ignored 1, needs-triage 1. https://ubuntu.com/security/CVE-2019-20477

Affected software / configurations for CVE-2019-20477

Vendor Product Version Raw CPE
pyyaml pyyaml >= 5.1, <= 5.1.2 cpe:2.3:a:pyyaml:pyyaml:*:*:*:*:*:*:*:*
fedoraproject fedora 30 cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
fedoraproject fedora 31 cpe:2.3:o:fedoraproject:fedora:31:*:*:*:*:*:*:*

References for CVE-2019-20477

cvelogic Threat Intelligence