Skip to main content

CircleCI Token

CircleCI tokens are authentication credentials used to access the CircleCI API and interact with CircleCI services. These tokens are critical for automating workflows, managing projects, and integrating with other tools. Exposure of a CircleCI token can lead to unauthorized access to your CI/CD pipelines, potentially allowing attackers to manipulate build processes, access sensitive environment variables, or deploy malicious code.

How Does It Look​

CircleCI tokens can appear in various contexts, such as:

  • Environment variables:

    export CIRCLECI_TOKEN="c1rcleci-t0ken-1234567890abcdef"

  • Configuration files (YAML):

    version: 2.1
    jobs:
      build:
        docker:
          - image: circleci/node:latest
        environment:
          CIRCLECI_TOKEN: c1rcleci-t0ken-1234567890abcdef

  • Code snippets:

    const circleciToken = "c1rcleci-t0ken-1234567890abcdef";

  • Connection strings (if applicable): Not typically used in connection strings.

Severity​

  • 🔴 Critical

CircleCI tokens are critical because they provide access to your CI/CD environment, which can include sensitive code, deployment configurations, and environment variables. An attacker with access to these tokens can manipulate build processes, potentially leading to unauthorized code execution or data exposure.

What Can an Attacker Do?​

With immediate access to a CircleCI token, an attacker can infiltrate your CI/CD pipeline, leading to severe security breaches.

Key actions an attacker can perform:

  • Modify build processes: Alter build scripts or configurations (if the token has write permissions).
  • Access sensitive environment variables: Extract secrets or credentials stored in the pipeline (if the token allows access to environment variables).
  • Deploy malicious code: Push unauthorized changes to production environments (if deployment permissions are granted).
  • Access project settings: View or change project configurations (if the token has admin privileges).

An attacker could potentially escalate their access by leveraging exposed secrets to move laterally within your infrastructure, compromising additional systems or services.

Real-World Impact​

Exposure of a CircleCI token poses significant business risks, including:

Primary impact includes unauthorized access to CI/CD pipelines.

Potential consequences include:

  • Data Exposure: Access to sensitive environment variables and secrets (if the token has read access to these variables).
  • Financial Loss: Costs associated with unauthorized resource usage or downtime (if deployment permissions are exploited).
  • Operational Disruption: Interruption of build and deployment processes (if the attacker modifies or halts pipelines).
  • Reputational Damage: Loss of trust from customers and partners due to security breaches.

In worst-case scenarios, attackers could gain persistent access to your infrastructure, leading to prolonged exploitation and damage.

Prerequisites for Exploitation​

To exploit a CircleCI token, an attacker needs:

  • Network access: Ability to interact with CircleCI's API endpoints.
  • Additional context: Knowledge of the specific CircleCI project or account associated with the token.
  • No rate limits: Exploitation is easier if there are no strict rate limits or IP restrictions in place.

How to Verify If It's Active​

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

curl -X GET https://circleci.com/api/v2/me -H "Circle-Token: [TOKEN]"

Valid credential response: A successful response will include user information, such as username and email.

Invalid/expired credential response: An error message indicating unauthorized access or invalid token.

Detection Patterns​

Common Variable Names:

  • CIRCLECI_TOKEN
  • CIRCLE_TOKEN
  • CIRCLE_CI_TOKEN
  • CCI_TOKEN
  • CIRCLECI_API_TOKEN
  • CIRCLECI_ACCESS_TOKEN

File Locations:

  • .circleci/config.yml
  • circleci.env
  • config.yml
  • build_config.yml

Regex Pattern:

circleci[-_]token\s*[:=]\s*["']?[a-zA-Z0-9_-]{20,40}["']?

Remediation Steps​

  1. Revoke immediately - Go to CircleCI > User Settings > Personal API Tokens and delete the compromised token.
  2. Audit access logs - Review CircleCI audit logs for unauthorized API calls or pipeline executions during the exposure window.
  3. Assess blast radius - Identify all systems, applications, and environments that used the exposed token.
  4. Rotate credential - Generate a new CircleCI token with least-privilege permissions.
  5. Update dependent systems - Deploy the new token to all applications and update CI/CD pipelines securely.
  6. Harden access controls - Enable IP allowlisting in CircleCI and require two-factor authentication for all users.
  7. Implement secrets management - Migrate tokens to a secrets manager (HashiCorp Vault, AWS Secrets Manager) to prevent hardcoding.
  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​