CVE-2017-18342

In PyYAML before 5.1, the yaml.load() API could execute arbitrary code if used with untrusted data. The load() function has been deprecated in version 5.1 and the 'UnsafeLoader' has been introduced for backward compatibility with the function.

Published: 2018-06-27 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2017-18342 is rated High Risk (70.9/100): CVSS Critical severity, with medium exploitation likelihood (EPSS 4.81%). High exploitation likelihood—assess exposure and prioritize remediation.

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

Exploit prediction scoring system (EPSS) score for CVE-2017-18342

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 2026-04-25 4.47% 4.81% +0.34%
2 2026-01-11 4.70% 4.47% -0.23%
3 2025-10-06 — 4.70% —

Full EPSS history (25 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2017-18342

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-2017-18342

GitHub Security Advisory for CVE-2017-18342

GHSA-rprw-h62v-c2w7 · Severity: critical · Ecosystem: pip — PyYAML insecurely deserializes YAML strings leading to arbitrary code execution

OS Trackers for CVE-2017-18342

vendor priority summary link
debian unimportant CVE-2017-18342 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-2017-18342
gentoo high CVE-2017-18342: 1 GLSA(s) (202003-45), 1 atom(s) (dev-python/pyyaml); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2017-18342
redhat high — https://access.redhat.com/security/cve/CVE-2017-18342
suse high CVE-2017-18342 severity important: SUSE including 303 source package names (amazon/suse-sles-15-sp1-chost-byos-v20210304-hvm-ssd-x86_64, amazon/suse-sles-15-sp1-chost-byos-v20220127-hvm-ssd-x86_64, …), 388 product×package rows across 69 product lines (HPE Helion OpenStack 8, Image SLES12-SP5-Azure-BYOS, … (69 product lines)): Known Affected 181, Fixed 147, Known Not Affected 60. https://www.suse.com/security/cve/CVE-2017-18342/
ubuntu low CVE-2017-18342 low priority: Ubuntu including 1 source packages (pyyaml), 8 status rows across 8 suites (bionic, cosmic, disco, eoan, focal, trusty, upstream, xenial): ignored 5, not-affected 2, needed 1. https://ubuntu.com/security/CVE-2017-18342

Affected software / configurations for CVE-2017-18342

Vendor Product Version Raw CPE
pyyaml pyyaml < 5.1 cpe:2.3:a:pyyaml:pyyaml:*:*:*:*:*:*:*:*
fedoraproject fedora 28 cpe:2.3:o:fedoraproject:fedora:28:*:*:*:*:*:*:*
fedoraproject fedora 29 cpe:2.3:o:fedoraproject:fedora:29:*:*:*:*:*:*:*
fedoraproject fedora 30 cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*

References for CVE-2017-18342

URL Tags
https://github.com/marshmallow-code/apispec/issues/278 Third Party Advisory
https://github.com/yaml/pyyaml/blob/master/CHANGES Release Notes Third Party Advisory
https://github.com/yaml/pyyaml/issues/193 Third Party Advisory
https://github.com/yaml/pyyaml/pull/74 Patch Third Party Advisory
https://github.com/yaml/pyyaml/wiki/PyYAML-yaml.load%28input%29-Deprecation
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JEX7IPV5P2QJITAMA5Z63GQCZA5I6NVZ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KSQQMRUQSXBSUXLCRD3TSZYQ7SEZRKCE/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/M6JCFGEIEOFMWWIXGHSELMKQDD4CV2BA/
https://security.gentoo.org/glsa/202003-45 Third Party Advisory
cvelogic Threat Intelligence