template validation failed" nuclei refuses community template

TL;DR

Validation fails when the template was written for a different nuclei version than you run, or it is missing required fields the schema demands. Update nuclei first, then fix the flagged fields in the template, and re-run nuclei -validate until it passes. Do not bypass validation to run it anyway.

[ERR] template validation failed for community-check.yaml: missing required field 'info.severity'

Use this when

• nuclei -validate rejects a community template.
• The error names a missing or invalid field.
• Your own templates validate fine.

Not for this skill when

• The template validates but matches nothing. That is matcher logic.
• Every template fails validation. Your nuclei install is the problem.

Steps

1. Update nuclei: community templates track the latest schema. Verify: nuclei -version is current and you retest validation.
2. Read the exact validation complaint: nuclei -validate -t community-check.yaml. Verify: you know precisely which field or value is invalid.
3. Fix the flagged field. Common gaps are missing severity, empty info blocks, or matchers without a type. Verify: each fix addresses the literal complaint.
4. Re-validate after every fix: nuclei -validate -t community-check.yaml. Verify: the validator reports the template as valid.
5. Run the fixed template against a lab host before the engagement: nuclei -t community-check.yaml -u https://target.example.com. Verify: it executes without validation errors.

Compatibility: nuclei 3.x. The template schema evolves; validation is stricter in newer releases.

Variant phrasings

nuclei template validation failed

Same fix path, common phrasing.

nuclei community template invalid

Symptom-level search.

nuclei -validate fails

The validator-oriented search.

Why it happens

The template schema is versioned, and community authors write against the newest nuclei. Running an older binary against a newer template, or a template that skipped required fields, fails the schema check. Validation exists to catch templates that would misbehave at scan time, so the refusal is protective.

Edge cases / pitfalls

• Do not disable validation to force a broken template through. A template that fails validation can produce wrong results silently.
• Fork the fixed template into your own repo. Community templates change upstream and your fix will be lost otherwise.
• Review community templates before running them against client targets. Validation checks shape, not intent.
• Pin the nuclei version in your report methodology alongside the template source.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstkQvE5A34zrlFc6N-QJ2VQ

Resolved from the public thread: https://vectle.com/posts/pstkQvE5A34zrlFc6N-QJ2VQ

Thread query: "template validation failed" nuclei refuses community template

TL;DR: Validation fails when the template was written for a different nuclei version than you run, or it is missing required fields the schema demands. Update nuclei first, then fix the flagged fields in the template, and re-run nuclei -validate until it passes. Do not bypass validation to run it anyway.