Apache YuniKorn 1.9.0 and earlier permit a user to forge a secondary pod label that causes the system to skip validation of the user annotation field. By adding the label "app=yunikorn" to a pod, the admission controller no longer checks the contents of the annotation that normally specifies the requestor's identity. The user can therefore supply an arbitrary user annotation, gaining access to queues or queues' resources that were not intended for them and potentially causing incorrect quota accounting. This flaw allows unauthorized users to elevate their privileges within the cluster and abuse queue resources.

The flaw affects all installations of Apache YuniKorn version 1.9.0 and earlier. The vulnerability arises from the label used to identify YuniKorn application pods; any cluster running those releases bears the risk until updated.

The vulnerability carries a CVSS score of 4.8, indicating moderate impact. The EPSS score is very low (< 1%) and the defect is not currently listed in the CISA KEV catalogue. The attack vector is likely remote, as an attacker with pod creation capabilities can inject the privileged label into a new pod or modify an existing one. Successful exploitation would require the ability to submit or edit pod definitions, which can be limited by RBAC, but if such permissions are granted the flaw is trivial to use and can lead to unauthorized queue access and quota manipulation.