Fuzzing is a form of vulnerability testing. But vulnerability testing is not necessary a form of fuzzing. Some vulnerability scanners might use fuzzing techniques, modules or plugins to do so. For example Nessus has the following plugins to approach "unknown" issues in web applications (source):
- 44967: CGI Generic Command Execution Vulnerability (time based)
- 44136: CGI Generic Cookie Injection Scripting
- 44135: Web Server Generic Cookie Injection
- 44134: CGI Generic Unseen Parameters Discovery
- 43160: CGI Generic SQL Injection (blind, time based)
- 42872: CGI Generic Local File Inclusion Vulnerability (2nd pass)
- 42479: CGI Generic SQL Injection Vulnerability (2nd pass)
- 42427: CGI Generic SQL Injection Vulnerability (HTTP Headers)
- 42426: CGI Generic SQL Injection Vulnerability (HTTP Cookies)
- 42425: CGI Generic Persistent Cross-Site Scripting Vulnerability
- 42424: CGI Generic SQL Injection (blind)
- 42423: CGI Generic SSI Injection Vulnerability
- 42056: CGI Generic Local File Inclusion Vulnerability
- 42055: CGI Generic Format String Vulnerability
- 42054: CGI Generic SSI Injection Vulnerability
- 39469: CGI Generic Remote File Inclusion Vulnerability
- 39468: CGI Generic Header Injection Vulnerability
- 39467: CGI Generic Path Traversal Vulnerability
- 39465: CGI Generic Command Execution Vulnerability
- 11139: CGI Generic SQL Injection Vulnerability
This helps to determine issues which are not covered by other plugins based on derivative techniques, fingerprinting mechanism or channeled exploit approaches.