This High severity DoS (Denial of Service) vulnerability known as CVE-2024-21634 was introduced in 9.12.1 of Jira Software 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 take actions which have no impact to confidentiality, no impact to integrity, high impact to availability, and requires no user interaction. 

Atlassian recommends that Jira Software 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 Software Data Center and Server 9.12: Upgrade to a release greater than or equal to 9.12.6

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

The National Vulnerability Database provides the following description for this vulnerability: Amazon Ion is a Java implementation of the Ion data notation. Prior to version 1.10.5, a potential denial-of-service issue exists in `ion-java` for applications that use `ion-java` to deserialize Ion text encoded data, or deserialize Ion text or binary encoded data into the `IonValue` model and then invoke certain `IonValue` methods on that in-memory representation. An actor could craft Ion data that, when loaded by the affected application and/or processed using the `IonValue` model, results in a `StackOverflowError` originating from the `ion-java` library. The patch is included in `ion-java` 1.10.5. As a workaround, do not load data which originated from an untrusted source or that could have been tampered with.