The Unauthenticated Exploit Path
A critical vulnerability in the Argo CD repo-server component allows unauthenticated attackers to execute arbitrary code, potentially leading to full Kubernetes cluster takeover. The flaw resides in the repo-server’s internal gRPC service, which lacks authentication. Any attacker who can reach this service on its network port can send a crafted request to run commands.
The exploit technique abuses kustomize, a standard tool used by Argo CD to process repository files into Kubernetes manifests. Kustomize has a –helm-command option pointing to the helm binary. An attacker can manipulate the GenerateManifest service to redirect this option to a malicious script from a controlled Git repository. When kustomize runs, it executes the attacker’s script instead of helm, granting code execution on the repo-server.
Impact and Scope
Researchers from Synacktiv, who discovered the bug, demonstrated that achieving code execution on the repo-server is just the beginning. From there, they extracted the Redis password from environment variables, connected to Argo CD’s Redis cache, and poisoned stored deployment data. On the next automatic sync, the cluster deployed attacker-controlled workloads. This technique effectively revives CVE-2024-31989, a previously patched flaw that allowed cache poisoning before Redis required authentication. The cache itself remains unsigned, so stealing the password reopens the same attack vector.
Argo CD ships with Kubernetes network policies designed to isolate the repo-server, but the Helm chart installs these policies with networkPolicy.create set to false by default. Without active policies, an attacker who compromises any single pod in the cluster can reach the repo-server and trigger the exploit. The maintainers were first notified in January 2025, but as of publication no patch or CVE has been released. Defenders must rely on enabling network policies to restrict access to the repo-server and Redis ports to only Argo CD’s own components.
Source: The Hacker News
