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

This Critical severity Business Logic vulnerability was introduced in versions 5.3.0, 6.0.0, 6.1.0, 6.2.0, 6.3.0, 7.0.1, 7.1.0 of Crowd Data Center.
 
This Business Logic vulnerability, with a CVSS Score of 9.1 and a CVSS Vector of VSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N allows an unauthenticated attacker to expose assets in your environment susceptible to exploitation which has high impact to confidentiality, high impact to integrity, no impact to availability, and requires no user interaction.
 
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 and Server 7.2: Upgrade to a release greater than or equal to 7.2.0

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-archive).
 
The National Vulnerability Database provides the following description for this vulnerability:

When applications specify HTTP response headers for servlet applications using Spring Security, there is the possibility that the HTTP Headers will not be written.  This issue affects Spring Security Servlet applications using lazy (default) writing of HTTP Headers: : from 5.7.0 through 5.7.21, from 5.8.0 through 5.8.23, from 6.3.0 through 6.3.14, from 6.4.0 through 6.4.14, from 6.5.0 through 6.5.8, from 7.0.0 through 7.0.3.