Skip to main content

Docker Swarm Token

Docker Swarm tokens are used to authenticate and authorize nodes joining a Docker Swarm cluster. These tokens are critical for maintaining the integrity and security of the cluster, as they control which nodes can participate in the swarm. Exposure of these tokens can lead to unauthorized access, allowing attackers to join the swarm, potentially compromising the entire cluster's operations and data.

How Does It Look​

Docker Swarm tokens can appear in various contexts, such as environment variables, configuration files, and code snippets. Here are some examples:

  • Environment Variables:

    export DOCKER_SWARM_TOKEN="SWMTKN-1-23abc456def-789ghi012jkl"

  • Configuration Files (.env):

    DOCKER_SWARM_TOKEN=SWMTKN-1-23abc456def-789ghi012jkl

  • Code Snippets:

    swarm_token = "SWMTKN-1-23abc456def-789ghi012jkl"

  • Connection Strings:

    docker swarm join --token SWMTKN-1-23abc456def-789ghi012jkl [MANAGER_IP]:2377

Severity​

  • 🔴 Critical

The severity of exposing a Docker Swarm token is critical because it grants the ability to join nodes to the swarm, potentially allowing unauthorized access to the cluster. This can lead to a complete compromise of the swarm's operations, data integrity, and availability, with a significant blast radius affecting all services running within the swarm.

What Can an Attacker Do?​

With immediate access to a Docker Swarm token, an attacker can join unauthorized nodes to the swarm, gaining a foothold within the cluster.

Key actions an attacker can perform:

  • Deploy Malicious Services: Deploy unauthorized services that can exfiltrate data or disrupt operations (if the token allows manager-level access).
  • Intercept Traffic: Capture and analyze network traffic between nodes (if network policies are not enforced).
  • Access Sensitive Data: Read or modify data stored within the swarm services (if the attacker gains access to data volumes).
  • Escalate Privileges: Attempt to gain higher privileges within the cluster (if additional vulnerabilities exist).

An attacker can use this access to move laterally within the network, potentially compromising other connected systems and services.

Real-World Impact​

The exposure of a Docker Swarm token poses significant business risks, including operational disruption and data breaches.

Potential consequences include:

  • Data Exposure: Sensitive data within the swarm could be accessed or exfiltrated (if the attacker gains access to data volumes).
  • Financial Loss: Increased costs due to unauthorized resource usage or service downtime (if the attacker deploys resource-intensive services).
  • Operational Disruption: Critical services could be disrupted or taken offline (if the attacker modifies or deletes services).
  • Reputational Damage: Loss of customer trust and brand reputation due to security breaches.

In the worst-case scenario, an attacker could gain control over the entire swarm, leading to cascading effects across all dependent services and systems.

Prerequisites for Exploitation​

To exploit a Docker Swarm token, an attacker needs:

  • Network Access: Ability to reach the Docker Swarm manager node.
  • Swarm Manager IP: Knowledge of the manager node's IP address.
  • Open Ports: Access to the swarm's communication ports (e.g., 2377 for cluster management).

How to Verify If It's Active​

To verify if a Docker Swarm token is active, use the following command:

docker swarm join --token [TOKEN] [MANAGER_IP]:2377

Valid credential response:

  • The node successfully joins the swarm, and you receive a confirmation message.

Invalid/expired credential response:

  • An error message indicating that the token is invalid or expired.

Detection Patterns​

Common Variable Names:

  • DOCKER_SWARM_TOKEN
  • SWARM_JOIN_TOKEN
  • SWARM_TOKEN
  • DOCKER_TOKEN
  • JOIN_TOKEN
  • SWARM_CLUSTER_TOKEN

File Locations:

  • .env
  • docker-compose.yml
  • config.json
  • swarm-config.yaml

Regex Pattern:

SWMTKN-[0-9]-[a-zA-Z0-9]{6,}-[a-zA-Z0-9]{6,}

Remediation Steps​

  1. Revoke immediately - Go to Docker Swarm manager and rotate the join token using docker swarm join-token rotate.
  2. Audit access logs - Review Docker daemon logs for unauthorized join attempts or suspicious activities during the exposure window.
  3. Assess blast radius - Identify all nodes and services that could have been affected by the exposed token.
  4. Rotate credential - Generate a new join token using docker swarm join-token manager or docker swarm join-token worker.
  5. Update dependent systems - Deploy the new token to all authorized nodes and update any scripts or configurations securely.
  6. Harden access controls - Implement network segmentation and firewall rules to restrict access to the swarm manager node.
  7. Implement secrets management - Store tokens securely using a secrets manager like HashiCorp Vault or AWS Secrets Manager.
  8. Add detection controls - Set up pre-commit hooks and repository scanning to catch token leaks before they reach production.

Credential exposures often go undetected for extended periods, increasing the window for exploitation. As a long-term strategy, plan to establish an internal process or engage an external vendor for continuous external exposure monitoring. This helps identify leaked secrets across public repositories, paste sites, dark web forums, and other external sources before attackers can leverage them. Proactive detection and rapid response are essential to minimizing the impact of credential leaks.

References​