Docker registry auth substring match forwards credentials to a different registry

Repository

cdxgen/cdxgen

Affected product/package

• Ecosystem: npm
• Package: @cyclonedx/cdxgen
• Reviewed tree version: 12.3.3
• Reviewed commit: b1e179869fd7c6032c3d483c3f7bd4d7154ec22b
• Affected file: lib/managers/docker.js
• Affected from: v9.9.5

The Single Executable Applications (SEA) binaries and container images are also affected.

Weakness

CWE-522 / CWE-346.

Summary

When cdxgen scans or pulls container images through the Docker daemon API, it builds an X-Registry-Auth header from Docker credentials in DOCKER_CONFIG/config.json. The credential selection logic matches configured registry keys with substring checks:

if (forRegistry && !serverAddress.includes(forRegistry)) {
  continue;
}

This is not an origin-safe registry comparison. For example, credentials configured for private-registry.example.com are selected for a requested image under registry.example.com, because:

"private-registry.example.com".includes("registry.example.com") === true

The selected credentials are then serialized into X-Registry-Auth for the Docker API pull request targeting the requested registry.

Reproduction

Use the attached/local proof:

node submissions/github-gsa/cdxgen-docker-registry-auth-substring-forwarding/evidence/cdxgen_docker_registry_auth_substring_probe.mjs

The proof is fully local. It creates a temporary Docker config containing credentials for private-registry.example.com, starts a localhost mock Docker API endpoint, sets DOCKER_HOST to that endpoint, then calls cdxgen's exported Docker request path for a pull from registry.example.com.

Observed vulnerable output:

{
  "decision": "GO",
  "dockerConfigAuthHost": "private-registry.example.com",
  "requestedRegistry": "registry.example.com",
  "substringMatch": true,
  "dockerApiUrl": "/images/create?fromImage=registry.example.com/team/app:latest",
  "headerPresent": true,
  "decodedHeader": {
    "username": "trusted-user",
    "password": "trusted-pass",
    "serveraddress": "private-registry.example.com"
  }
}

Impact

If an operator has Docker credentials for a private registry and uses cdxgen to scan an image from a different registry whose hostname is a substring of that private registry hostname, cdxgen can attach the private registry credentials to the Docker pull request for the different registry.

In a realistic attack, an attacker who controls or can observe the requested registry can induce a victim to scan an image from that registry. The Docker daemon API receives an X-Registry-Auth payload containing credentials for the victim's private registry but associated with the attacker-requested pull. This is a credential forwarding/misbinding issue in cdxgen's container image handling.

References

Functions normalizeRegistryHost and registriesMatch added to normalize and perform strict host matching.

Fix PR: https://github.com/cdxgen/cdxgen/pull/3964

Researcher: Francesco SabiuResearcher: Francesco Sabiu