Argo CD is a declarative, GitOps continuous delivery tool for Kubernetes. This report details a security vulnerability in Argo CD, where an unauthenticated attacker can send a specially crafted large JSON payload to the /api/webhook endpoint, causing excessive memory allocation that leads to service disruption by triggering an Out Of Memory (OOM) kill. The issue poses a high risk to the availability of Argo CD deployments. This vulnerability is fixed in 2.11.6, 2.10.15, and 2.9.20.