Nuclei

Nuclei is a template-driven, high-performance vulnerability scanner written in Go, designed to probe modern applications, infrastructure, and networks for exploitable security flaws. At its core, each scan is defined by a YAML template that specifies the protocol to use (HTTP, TCP, DNS, SSL, WebSocket, etc.), the exact requests or probes to send, and the matchers that determine a positive finding. This architecture means detection logic is transparent, auditable, and trivially shareable — security researchers can write a template for a new CVE in minutes and distribute it to thousands of users via the community repository.

The engine is built for speed and scale. Nuclei processes targets in parallel with request clustering and deduplication to avoid redundant network calls, making it practical for scanning large attack surfaces. Templates are organised by severity, protocol, and type (CVE, misconfiguration, exposure, takeover, default-creds, etc.) and can be composed into multi-step workflows that chain probes together, supporting complex exploit chains or authenticated scan sequences with JWT, API key, or basic auth credential injection.

What makes Nuclei stand out is the combination of community velocity and engineering rigour. The template library is the most actively maintained open detection corpus in the industry, with a formal bounty program incentivising researchers to contribute templates for newly disclosed vulnerabilities — often within hours of a CVE publication. Because templates reproduce actual attacker behaviour rather than relying on version banners, findings are highly actionable with low false-positive rates. With 27,000+ GitHub stars, Nuclei has become one of the most widely adopted open-source security tools in both bug bounty and enterprise AppSec pipelines.