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NuGet API Key

NuGet API keys are used to authenticate and authorize access to the NuGet package repository, a popular platform for managing and distributing .NET packages. These keys allow developers to publish, update, and manage packages in the NuGet ecosystem. Exposure of a NuGet API key can lead to unauthorized access to your package repository, potentially allowing attackers to upload malicious packages or tamper with existing ones, posing a significant security risk.

How Does It Look​

NuGet API keys can appear in various contexts, such as:

  • Environment variables

    export NUGET_API_KEY="nuget-1234567890abcdef"

  • Configuration files (.env)

    NUGET_API_KEY=nuget-1234567890abcdef

  • Code snippets

    var apiKey = "nuget-1234567890abcdef";

  • Connection strings

    https://api.nuget.org/v3/index.json?apikey=nuget-1234567890abcdef

Severity​

  • 🟠 High

The severity of a NuGet API key exposure is high because it grants the ability to publish and manage packages in the NuGet repository. An attacker with this key can upload malicious packages, potentially affecting all users who download them. The blast radius includes any systems or applications that rely on the compromised packages.

What Can an Attacker Do?​

With immediate access to a NuGet API key, an attacker can manipulate the package repository:

  • Publish malicious packages: Upload harmful code to the repository (if the key has publish permissions).
  • Modify existing packages: Alter package contents or metadata (if the key allows updates).
  • Delete packages: Remove packages from the repository, disrupting dependent applications (if delete permissions are granted).
  • Access package statistics: View download and usage statistics (if the key has read access).

An attacker could escalate their impact by introducing vulnerabilities into widely used packages, potentially leading to further compromise of systems that integrate these packages.

Real-World Impact​

The exposure of a NuGet API key poses significant business risks:

  • Data Exposure: Unauthorized access to package metadata and statistics (if the key has read access).
  • Financial Loss: Costs associated with mitigating the impact of malicious packages and potential legal liabilities (if harmful packages are distributed).
  • Operational Disruption: Breakage of applications relying on compromised packages (if packages are deleted or altered).
  • Reputational Damage: Loss of trust from users and partners due to compromised package integrity.

In a worst-case scenario, the introduction of vulnerabilities into critical packages could lead to widespread exploitation across multiple organizations.

Prerequisites for Exploitation​

To exploit a NuGet API key, an attacker needs:

  • Network access: Ability to connect to the NuGet repository.
  • Repository endpoint: Knowledge of the specific NuGet repository URL.
  • No IP restrictions: The key must not be restricted by IP allowlisting.

How to Verify If It's Active​

To verify if a NuGet API key is active, use the following command:

curl -X GET "https://api.nuget.org/v3/index.json" -H "X-NuGet-ApiKey: [API_KEY]"

Valid credential response:

  • Successful response with package metadata or status code 200.

Invalid/expired credential response:

  • Error message or status code 401/403 indicating unauthorized access.

Detection Patterns​

Common Variable Names:

  • NUGET_API_KEY
  • NUGET_KEY
  • API_KEY
  • NUGET_TOKEN
  • NUGET_SECRET
  • NUGET_ACCESS_KEY

File Locations:

  • .env
  • appsettings.json
  • nuget.config
  • config.yml

Regex Pattern:

nuget-[a-f0-9]{16,32}

Remediation Steps​

  1. Revoke immediately - Go to NuGet.org > Account Settings > API Keys and delete the compromised key.
  2. Audit access logs - Review NuGet repository logs for unauthorized package uploads or modifications during the exposure window.
  3. Assess blast radius - Identify all systems, applications, and environments that used the exposed API key.
  4. Rotate credential - Generate a new API key in NuGet.org with least-privilege permissions.
  5. Update dependent systems - Deploy the new API key to all applications and update CI/CD pipelines securely.
  6. Harden access controls - Enable IP allowlisting in NuGet.org and require additional authentication measures.
  7. Implement secrets management - Migrate API keys 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 API key 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​