Drupal core 8 before versions 8.3.4 allows remote attackers to execute arbitrary code due to the PECL YAML parser not handling PHP objects safely during certain operations.
https://www.drupal.org/forum/newsletters/security-advisories-for-drupal-core/2017-06-21/drupal-core-multiple
http://www.securitytracker.com/id/1038781
http://www.securityfocus.com/bid/99211
Source: Mitre, NVD
Published: 2018-08-06
Updated: 2018-10-04
Base Score: 7.5
Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P
Severity: High
Base Score: 9.8
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Severity: Critical