What is Nuclei?

Nuclei is an open-source vulnerability scanner developed by ProjectDiscovery. It uses a template-based approach where each detection check is defined in a YAML file, making it fast to extend and community-driven. The public template library contains over 8,000 templates covering CVEs, misconfigurations, default credentials, exposed panels, and information disclosures.

How Nuclei works

Nuclei sends crafted HTTP requests (or DNS, TCP, and other protocol requests) to targets and matches responses against patterns defined in templates. Each template specifies the request to send, the response pattern to match, and metadata including severity and CVE references.

nuclei -u https://example.com -t cves/ -severity critical,high

Nuclei is widely used for external attack surface scanning because it is fast (Go-based, highly concurrent), accurate (template-based matching reduces false positives compared to version-string-only detection), and extensible (anyone can write templates for new CVEs or checks). Many EASM platforms, including SurfaceLoop, use Nuclei templates as one input to their detection engines.

Map your attack surface - first scan free