Fuzzing Capabilities
Relevant source files
The following files were used as context for generating this wiki page:
OWASP Nettacker incorporates a modular fuzzing engine designed to automate the discovery of vulnerabilities such as misconfigurations, information leakage, and Remote Code Execution (RCE). The engine allows for dynamic payload generation by injecting various data sets into specific parts of a network request, including URLs, headers, and request bodies. This capability is central to the project's goal of providing automated penetration testing and information gathering.
Sources: README.md, nettacker/core/fuzzer.py
Fuzzing Engine Architecture
The fuzzing system operates by taking a base template (often defined in YAML) and expanding it into multiple unique requests. It uses a structured input format that supports placeholders for targets, schemas, and ports. The engine iterates through defined data sets—such as different protocols (HTTP/HTTPS) or port lists—to permute every possible combination for a given target.
The diagram shows the transition from static module definitions to dynamic request generation and subsequent validation.
Sources: nettacker/core/fuzzer.py, nettacker/modules/vuln/nextjs_cve_2025_55182.yaml
Components and Logic
The fuzzer is responsible for the following core logic:
- Placeholder Replacement: Variables like
{target}and{user_agent}are dynamically replaced with active session data or randomized values. - Permutation Handling: The engine processes nested data structures (e.g., schemas and ports) to ensure comprehensive coverage of a target's attack surface.
- Interceptors: Specific functions (like
generate_and_replace_md5) can be invoked to transform data before it is sent.
Sources: nettacker/core/fuzzer.py:1-50, nettacker/modules/vuln/wp_plugin_cve_2021_38314.yaml
YAML-Based Fuzzing Definitions
Fuzzing tasks are primarily defined in YAML files located within the nettacker/modules/ directory. These files define the metadata, payloads, and the expected successful response conditions.
Payload Structure
A fuzzing payload typically contains:
| Field | Description |
|---|---|
method | The HTTP method used (GET, POST, etc.). |
url | The template URL utilizing nettacker_fuzzer for permutations. |
headers | Custom headers, which themselves can be fuzzed (e.g., Origin headers). |
data | The request body, supporting complex multipart or JSON structures. |
interceptors | Custom processing logic for specific fields. |
Sources: nettacker/modules/vuln/http_cors.yaml, nettacker/modules/vuln/nextjs_cve_2025_55182.yaml
Example: Next.js RCE Fuzzing
In the nextjs_cve_2025_55182.yaml module, the fuzzer is used to test for RCE by sending complex multipart/form-data. It targets various schemas and ports while injecting specific flight protocol payloads.
url:
nettacker_fuzzer:
input_format: "{{schema}}://{target}:{{ports}}/"
data:
schema:
- "http"
- "https"
ports:
- 80
- 443
Sources: nettacker/modules/vuln/nextjs_cve_2025_55182.yaml:45-56
Response Validation and Conditions
The effectiveness of the fuzzing engine relies on its ability to accurately identify "hits" based on server responses. The framework supports complex logic for validation using condition_type (e.g., and, or).
Validation Criteria
- Status Codes: Checking for specific codes like
200 OK. - Header Regex: Matching headers such as
Access-Control-Allow-Originorx-action-redirect. - Content Regex: Inspecting the response body for specific patterns like MD5 hashes or specific redirect strings.
This sequence illustrates the feedback loop between the fuzzer and the target to determine vulnerability status.
Sources: nettacker/modules/vuln/http_cors.yaml, nettacker/locale/en.yaml
Advanced Fuzzing Features
Interceptors
Interceptors allow for programmatic manipulation of fuzzing inputs. For instance, the wp_plugin_cve_2021_38314 module uses the generate_and_replace_md5 interceptor to create valid hashes for the URL path based on the current target.
Sources: nettacker/modules/vuln/wp_plugin_cve_2021_38314.yaml:27-30
HTTP CORS Fuzzing
The http_cors.yaml module demonstrates the fuzzer's ability to manipulate headers. It tests for CORS misconfigurations by fuzzing the Origin header with various patterns:
- Pre-domain (e.g.,
example.com.{target}) - Post-domain (e.g.,
{target}.example.com) - Null origins and wildcards
Sources: nettacker/modules/vuln/http_cors.yaml:15-150
Summary
The fuzzing capabilities in OWASP Nettacker provide a flexible, YAML-driven framework for automated security testing. By combining template-based request generation with protocol-aware permutations and response regex validation, the system can efficiently scan for a wide variety of vulnerabilities across different network services and web applications.