42Crunch for Mobile backend BOLA testing

42Crunch is a black-box API security scanner designed to detect Broken Object Level Authorization (BOLA) patterns without requiring code instrumentation or access to your source repository. It submits requests through public endpoints, analyzes responses for indicators of ID enumeration and adjacent ID probing, and maps findings to the OWASP API Top 10 (2023). The scanner does not attempt to modify or repair backend logic; it surfaces risk scores and prioritized findings to help security teams decide where deeper manual review is needed.

The scanner exercises BOLA by probing sequential and adjacent identifiers using read-only methods such as GET and HEAD. It looks for differences in response codes, body content, and timing that suggest an application returns data for neighboring IDs. Detection includes:

• Sequential ID enumeration across numeric or UUID-like path parameters.
• Active adjacent-ID probing where the scanner iterates nearby values and compares responses.
• Analysis of rate-limit headers and response sizes to infer whether unauthorized access is tolerated.

Findings include confidence indicators and remediation guidance, such as enforcing strict ownership checks on the server side and replacing predictable identifiers with opaque references.

Authenticated scans increase coverage for BOLA scenarios where endpoints require tokens or cookies. Supported credentials include Bearer tokens, API keys, Basic auth, and session cookies. Before scanning with credentials, domain verification is enforced through DNS TXT records or an HTTP well-known file to ensure only the domain owner can submit authenticated checks. The scanner forwards only a strict header allowlist:

Authorization
X-API-Key
Cookie
X-Custom-*

This approach limits exposure while allowing the scanner to exercise authorization boundaries that would otherwise trigger BOLA.

42Crunch offers multiple integration paths to fit into existing development and security workflows. The CLI allows on-demand scans from a terminal with JSON or text output, suitable for scripting and local verification. A GitHub Action can gate CI/CD pipelines, failing a build when the score drops below a configured threshold. The MCP server enables scanning from AI coding assistants, and the web dashboard centralizes reports and score trend tracking. All integrations use the same read-only scanning engine and share the same authentication and header allowlist behavior.

Because the scanner is restricted to read-only methods, it cannot test business logic that requires stateful write operations or complex multi-step workflows. It does not perform intrusive payloads such as active SQL injection or command injection, and it cannot detect blind SSRF or subtle logic flaws that depend on domain-specific behavior. These gaps mean the tool should be part of a broader strategy that includes manual code review, targeted threat modeling, and periodic human-led penetration tests for high-risk APIs.