This is a vulnerability in a non-Atlassian Jira dependency. Atlassian's application of this dependency presents a lower, non-critical assessed risk.

This Critical severity RCE (Remote Code Execution) vulnerability was introduced in versions 11.3.3 of Jira Software Data Center.

This RCE (Remote Code Execution) vulnerability, with a CVSS Score of 9.8 and a CVSS Vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H allows an unauthenticated attacker to potentially execute arbitrary code on the remote system which has high impact to confidentiality, high impact to integrity, high impact to availability, and requires no user interaction.

Atlassian recommends that Jira Software Data Center customers upgrade to latest version, if you are unable to do so, upgrade your instance to one of the specified supported fixed versions:

• Jira Software Data Center 11.3: Upgrade to a release greater than or equal to 11.3.4

 
See the release notes (https://www.atlassian.com/software/jira/download-archives). You can download the latest version of Jira Software Data Center from the download center (https://confluence.atlassian.com/jirasoftware/jira-software-release-notes-776821069.html).
The National Vulnerability Database provides the following description for this vulnerability: SnakeYaml's Constructor() class does not restrict types which can be instantiated during deserialization. Deserializing yaml content provided by an attacker can lead to remote code execution. We recommend using SnakeYaml's SafeConsturctor when parsing untrusted content to restrict deserialization. We recommend upgrading to version 2.0 and beyond.