This High severity Apache Tomcat vulnerability was introduced in version 5.3.0 of Crowd Data Center.

This Apache Tomcat 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 attacker to expose assets in your environment susceptible to exploitation.

Atlassian recommends that Crowd 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:

Crowd Data Center 5.3: Upgrade to a release greater than or equal to 5.3.8
Crowd Data Center 6.0: Upgrade to a release greater than or equal to 6.0.10
Crowd Data Center 6.1: Upgrade to a release greater than or equal to 6.1.6
Crowd Data Center 6.3: Upgrade to a release greater than or equal to 6.3.2
See the release notes (https://confluence.atlassian.com/crowd/crowd-release-notes-199094.html). You can download the latest version of Crowd Data Center from the download center (https://www.atlassian.com/software/crowd/download/data-center).

The National Vulnerability Database provides the following description for this vulnerability: Uncontrolled Resource Consumption vulnerability in Apache Tomcat if an HTTP/2 client did not acknowledge the initial settings frame that reduces the maximum permitted concurrent streams. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.8, from 10.1.0-M1 through 10.1.42, from 9.0.0.M1 through 9.0.106. The following versions were EOL at the time the CVE was created but are known to be affected: 8.5.0 through 8.5.100. Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.