strongSwan versions 5.1.3 through 6.0.7 contain an infinite loop vulnerability in the x509 plugin's attribute certificate parser when processing ietfAttrSyntax values. This flaw can be triggered remotely to cause the software to consume excessive resources, resulting in a denial of service condition. The vulnerability has a CVSS 3.1 score of 7.5, indicating a medium severity impact. Official patches addressing this issue are available in updated Ubuntu package versions.