This High severity Third-Party Dependency vulnerability was introduced in versions 5.2.0, 5.1.5, 5.0.7, 4.4.5, and other older versions of Crowd 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 Crowd 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:

• Crowd Data Center and Server 5.2: Upgrade to a release greater than or equal to 5.2.1
• Crowd Data Center and Server 5.1: Upgrade to a release greater than or equal to 5.1.6
• Crowd Data Center and Server 5.0: Upgrade to a release greater than or equal to 5.0.8

See the release notes (https://confluence.atlassian.com/crowd/crowd-release-notes-199094.html). You can download the latest version of Crowd Data Center and Server from the download center (https://www.atlassian.com/software/crowd/download-archive).

The National Vulnerability Database provides the following description for this vulnerability: The HTTP/2 protocol allows a denial of service (server resource consumption) because request cancellation can reset many streams quickly, as exploited in the wild in August through October 2023.