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Threat Research · wiz.io

Red Agent Chains SSRF and URL-Validation Bypass to Read GCP Cloud Run Files

· Original article ↗

Summary

Wiz describes how its Red Agent bypassed a GitHub URL validator in a GCP Cloud Run service to read local files, exposing service-account credentials and application source code.

Key points

  • The Cloud Run endpoint accepted a user-controlled URL but attempted to restrict requests to GitHub blob URLs.
  • After failed traversal and URL-confusion attempts, the agent used a double slash followed by an absolute path to bypass validation.
  • The flaw enabled unauthenticated reads of /proc/self/environ and application files, including source code.
  • The exposed environment contained GCP service-account credentials and API keys; Wiz says the credentials worked against live GCP APIs.
  • Wiz reports that the agent reached the exploit through 96 probing requests that built on earlier failures.

Article Details

Attack Vectors
  • An unauthenticated SSRF in a GCP Cloud Run service accepted a URL parameter restricted to GitHub blob URL structure.
  • Appending // and an absolute filesystem path after a valid-looking GitHub URL bypassed the validator and enabled local file reads.
  • The file-read primitive exposed service-account credentials and API keys from /proc/self/environ, as well as application source code and bundle metadata.

MITRE ATT&CK

T1005 · Data from Local SystemThe exploit read local files, including /proc/self/environ and application source code.T1190 · Exploit Public-Facing ApplicationThe Red Agent exploited an SSRF vulnerability in a production GCP Cloud Run API.

Vendors

Googlefirst move was to test whether it could redirect that fetch to the GCP metadata server at http://metadata.google.internal/computeMetadata/v1/instance/service-accounts/default/token- the fastest path to credential theft

Products

GCPIn this exploit, the Red Agent found a critical multi-step attack chain that allowed SSRF-to-Local-File-Read on a GCP Cloud Run API.Google Cloud RunIn this exploit, the Red Agent found a critical multi-step attack chain that allowed SSRF-to-Local-File-Read on a GCP Cloud Run API.

Tools

Red AgentFor the first deep-dive blog in our Red Agent POV series we will focus on a Server-Side Request Forgery (SSRF) exploit discovered by the Red Agent, which is one of the most common and impactful bug classes in modern

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