Cent: Aggregating 3,000+ Community Nuclei Templates Without Losing Your Mind

Hook

There are over 500 GitHub repositories hosting custom Nuclei templates, but ProjectDiscovery's official collection contains fewer than 2,000 templates. The community has written thousands more—they're just scattered everywhere.

Context

Nuclei, ProjectDiscovery's vulnerability scanner, relies on YAML templates to detect security issues. While the official nuclei-templates repository is well-maintained and curated, it represents only a fraction of what the security community has built. Bug bounty hunters and penetration testers have created specialized templates for obscure CVEs, niche technologies, and zero-day vulnerabilities that will never make it into the official collection—either because they're too specific, experimental, or simply haven't been submitted.

The fragmentation problem is real. A researcher hunting for vulnerabilities in a specific CMS might need to manually clone a dozen different repositories, each maintained by different security researchers with varying naming conventions and directory structures. Keeping these updated becomes a maintenance nightmare. Cent emerged as a practical solution: a Go-based aggregator that treats community templates as a distributed package ecosystem, pulling them into a unified directory structure that Nuclei can scan efficiently.

Technical Insight

Cent's architecture is deceptively simple but thoughtfully designed. At its core, it's a concurrent repository cloner with filtering intelligence. The tool maintains a YAML configuration file (cent.yaml) that lists GitHub repositories containing Nuclei templates. Here's what a typical configuration entry looks like:

repositories:
  - url: https://github.com/projectdiscovery/nuclei-templates
    exclude:
      - ".git"
      - "README.md"
  - url: https://github.com/geeknik/nuclei-templates-1
  - url: https://github.com/pikpikcu/nuclei-templates
    exclude:
      - "workflows/"

When you run cent update, it spawns configurable goroutines (default 10 threads) to clone these repositories concurrently into ~/cent-nuclei-templates/. The threading model is straightforward—each repository gets its own goroutine, bounded by a semaphore to prevent overwhelming your system or triggering GitHub's rate limits. This is Go's sweet spot: lightweight concurrency that doesn't require complex async/await patterns.

The interesting design decision is how Cent handles incremental updates. Rather than implementing git pull operations, it takes a nuclear approach: if a repository already exists locally, it removes the entire directory and re-clones. This sounds wasteful, but it elegantly sidesteps git merge conflicts, detached HEAD states, and the complexity of tracking multiple branches. For template aggregation, where you're not contributing changes back upstream, this trade-off makes sense. The exclusion logic runs post-clone, walking the directory tree and removing unwanted files:

for _, exclude := range repo.Exclude {
    excludePath := filepath.Join(repoPath, exclude)
    if _, err := os.Stat(excludePath); err == nil {
        os.RemoveAll(excludePath)
    }
}

Cent's summary command demonstrates why template aggregation matters. It recursively parses all YAML templates, extracting metadata like CVE IDs, severity levels, and tags. The output reveals coverage gaps:

$ cent summary
Total templates: 3,247
CVEs covered: 1,543
Severity distribution:
  critical: 127
  high: 489
  medium: 1,205
  low: 1,426
Top tags: cve, exposure, panel, takeover, xss

This analytics capability is valuable for understanding your attack surface coverage. If you're testing an e-commerce platform and see only 12 templates tagged with "magento," you know where your blind spots are. The JSON output mode (--json) makes it trivial to pipe this into monitoring dashboards or integrate with CI/CD pipelines.

The repository health check feature (cent check) addresses a real operational pain point. Community repositories disappear—maintainers abandon projects, accounts get deleted, repos go private. Cent will test-connect to each repository URL and flag dead sources:

$ cent check
[✓] projectdiscovery/nuclei-templates
[✗] olduser/deleted-repo (404: Not Found)
[✓] geeknik/nuclei-templates-1

You can automatically purge these with --remove, keeping your configuration clean. This is the kind of unglamorous maintenance feature that separates hobbyist tools from production-ready ones. The implementation is straightforward HTTP HEAD requests with timeout handling, but the user experience improvement is substantial when you're managing 50+ template sources.

Gotcha

Cent's biggest limitation is its complete lack of quality control. When you aggregate hundreds of community repositories, you're inheriting every bad practice, outdated template, and false positive those authors produced. I've seen templates that haven't been updated in three years still checking for vulnerabilities in software versions nobody runs anymore. You'll also encounter duplicates—the same CVE-2021-44228 (Log4Shell) template exists in dozens of repositories with slight variations, meaning Nuclei will scan the same vulnerability multiple times.

The disk space requirements are non-trivial. Because Cent clones full git repositories (including .git directories unless explicitly excluded), you'll easily consume 500MB-1GB depending on how many sources you track. Each repository's entire commit history comes along for the ride, even though you only care about the current templates. A more efficient architecture would shallow clone (--depth 1) or extract only YAML files, but Cent doesn't offer these options. Additionally, GitHub rate limiting can bite you. If you're aggregating 50+ repositories and run cent update multiple times in quick succession, you might hit API limits even with authenticated requests. The tool doesn't implement exponential backoff or sophisticated retry logic—it just fails.

Verdict

Use Cent if you're a bug bounty hunter or penetration tester who needs maximum template coverage and can tolerate false positives. It's particularly valuable when targeting niche technologies, hunting for recently disclosed CVEs that haven't made it into official collections, or conducting comprehensive reconnaissance where breadth matters more than precision. The summary analytics alone justify the setup cost if you're managing large template collections. Skip it if you're building automated security pipelines where false positives create alert fatigue, working in disk-constrained environments, or prioritizing template quality over quantity. For most security teams, the official nuclei-templates repository plus 5-10 carefully curated community sources will provide better signal-to-noise than indiscriminate aggregation. Cent is a power tool for experts who know how to filter wheat from chaff, not a beginner-friendly solution.