CVE-2026-50566: Fission: Environment Runtime.Container and Builder.Container SecurityContext bypass allows privileged pod creation

Synopsis

This is a security-context bypass in Fission, the open-source Kubernetes-native serverless framework. An authenticated user with permission to create or update Fission Environment resources can craft a malicious Environment manifest that injects privileged container settings, causing Fission's executor to schedule pods that run with elevated Kubernetes privileges under the executor's high-privilege service account. Successful exploitation grants the attacker container-sandbox escape, access to host filesystems and host networking, and the ability to pivot to node-level and cluster-level compromise. HarborGuard is tracking this advisory and will make a patched-image rebuild available as soon as version 1.24.0 or a subsequent fix is published upstream.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must reach the Fission API server over the network to submit a malicious Environment manifest.

• AuthenticationRequired

  A low-privilege account holding environments.fission.io create or update RBAC rights is sufficient; no admin credentials are needed.

• Victim interactionNot required

  No user interaction is needed; the exploit is triggered entirely by the attacker submitting the crafted manifest.

• Attack complexityDetail

  Exploit conditions are reliable and free of environmental dependencies; no race conditions or special memory layout requirements exist.

Blast Radius

• Attacker escapes the container sandbox and gains access to the host node's filesystem, including secrets, credentials, and kubeconfig files mounted or stored on the node.
• Attacker accesses host networking, enabling traffic interception and lateral movement to other pods and services on the node's network interfaces.
• Attacker operates under the executor's high-privilege service account, allowing Kubernetes API calls that can read, modify, or delete resources across namespaces.
• Attacker can achieve full cluster compromise by leveraging node-level access and the bound service account token to escalate control plane privileges.