This High severity Third-Party Dependency vulnerability was introduced in versions 4.20.0, 5.5.0, 5.6.0, 5.7.0, 5.8.0, 5.9.0, 5.10.0, and 5.11.0 of Jira Service Management Data Center and Server.

This Third-Party Dependency vulnerability, with a CVSS Score of 7.5 and a CVSS Vector of CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H allows an unauthenticated attacker to expose assets in your environment susceptible to exploitation which has no impact to confidentiality, no impact to integrity, high impact to availability, and requires no user interaction.

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

• Jira Service Management Data Center and Server 4.20: Upgrade to a release greater than or equal to 4.20.27

See the release notes (https://confluence.atlassian.com/servicemanagement/jira-service-management-release-notes-780083086.html). You can download the latest version of Jira Service Management Data Center and Server from the download center (https://www.atlassian.com/software/jira/service-management/download-archives).

The National Vulnerability Database provides the following description for this vulnerability: [Json-smart](https://netplex.github.io/json-smart/) is a performance focused, JSON processor lib. When reaching a ‘[‘ or ‘{‘ character in the JSON input, the code parses an array or an object respectively. It was discovered that the code does not have any limit to the nesting of such arrays or objects. Since the parsing of nested arrays and objects is done recursively, nesting too many of them can cause a stack exhaustion (stack overflow) and crash the software.