Is 42Crunch good for LLM gateway boundary test?

An LLM gateway boundary test focuses on the interaction surface where untrusted prompts enter an LLM processing chain. Tests verify that system prompts are not extractable, that jailbreak and injection probes are contained, and that tool-use paths do not leak sensitive data or enable unintended actions. The goal is to validate guardrails, not to replace adversarial red teaming that requires domain context.

middleBrick performs black-box scanning with read-only methods and text-only POST capabilities suitable for LLM probes. It runs 18 adversarial probes across three scan tiers focused on system prompt extraction, instruction override, DAN and roleplay jailbreaks, data exfiltration, cost exploitation, encoding bypasses, translation-embedded injection, few-shot poisoning, markdown injection, multi-turn manipulation, indirect prompt injection, token smuggling, tool-abuse, nested instruction injection, and PII extraction. The scanner maps findings to OWASP API Top 10 (2023), which covers common LLM security control failures such as improper input validation and unsafe output handling.

middleBrick supports OpenAPI analysis and can parse definitions to detect undefined security schemes or deprecated operations that may affect gateway routing. It validates controls referenced in OWASP API Top 10 (2023) relevant to prompt injection and unsafe consumption surfaces. It does not perform active SQL injection or command injection, does not detect business logic vulnerabilities that require domain understanding, and does not detect blind SSRF that relies on out-of-band infrastructure. It also does not replace a human pentester for high-stakes audits or provide evidence for compliance certifications such as HIPAA, GDPR, ISO 27001, SOC 2, or other frameworks; it only helps prepare audit evidence and aligns with security controls described in those standards where applicable.

Authenticated scanning is available for Bearer, API key, Basic auth, and Cookie methods, gated by domain verification to ensure only domain owners submit credentials. Header forwarding is limited to an allowlist including Authorization, X-API-Key, Cookie, and X-Custom-* headers. For LLM gateway tests, credentials should only be used when the domain ownership condition is met, and sensitive headers are restricted to minimize risk. The scanner operates read-only and blocks private IPs, localhost, and cloud metadata endpoints at multiple layers.

When the assessment requires active exploit capabilities such as SQL injection or command injection against the LLM gateway, middleBrick is not sufficient. Consider using specialized adversarial testing platforms or engage a human red team that can design custom payloads and validate business logic around prompt injection, data leakage, and tool abuse in the context of your specific gateway implementation.