This High severity DoS (Denial of Service) vulnerability was introduced in versions 10.2.0, 10.3.0, 10.4.0, and 10.5.0 of Jira Service Management Data Center and Server.

This 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 10.3: Upgrade to a release greater than or equal to 10.3.6

See the release notes. You can download the latest version of Jira Service Management Data Center and Server from the download center.

The National Vulnerability Database provides the following description for this vulnerability: path-to-regexp turns path strings into a regular expressions. In certain cases, path-to-regexp will output a regular expression that can be exploited to cause poor performance. Because JavaScript is single threaded and regex matching runs on the main thread, poor performance will block the event loop and lead to a DoS. The bad regular expression is generated any time you have two parameters within a single segment, separated by something that is not a period (.). For users of 0.1, upgrade to 0.1.10. All other users should upgrade to 8.0.0.