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Certificate uses an unusually broad wildcard

LowHigh confidencetls.certificate.wildcard-too-broad

What this check looks for

The certificate covers a very wide range of names. If its private key ever leaks, the damage extends far beyond this one site.

Why it matters

A wildcard's blast radius is every name it covers. One compromised server means every host under that wildcard can be impersonated, and re-issuing means touching all of them at once.

When the check passes, your report says: “Any wildcard in the certificate is narrow in scope”.

What it costs your score

When this check fails it removes 4 points from your TLS score, before the status, confidence and repeat multipliers are applied. TLS carries a weight of 15 in the overall score.

It shares the tls.certificate family ceiling of 60 points: however many findings that family produces, together they cannot remove more than that from TLS. One underlying problem showing up in several places is still one problem.

Severity
low
Default confidence
high
Status when triggered
warn
Deduction
4 points
Family cap
tls.certificate · 60
Category
TLS
Module
Tls certificate
Fix owned by
user
In the ruleset since
2026.09

How the whole score is calculated

How to fix it

Narrow the certificate to the hostnames this server actually serves.

A leaked key for a broad wildcard compromises every name under it at once.

  1. List the hostnames served by this host and issue a certificate naming them.

  2. Keep a wildcard only where names are genuinely created dynamically.

How to confirm it worked

  • openssl s_client -connect ‹host›:443 -servername ‹host› </dev/null 2>/dev/null | openssl x509 -noout -ext subjectAltName

A named slot like ‹domain› — and the braces left in the configuration below — is filled in with your own values when this rule appears on a report.

Remediation by platform

nginx
certbot --nginx -d ‹host› --cert-name ‹host›
Technical detail

The certificate for ‹host› presents ‹wildcard›, which sits at or above the registrable-domain boundary. RFC 6125 §6.4.3 permits a wildcard only in the leftmost label and warns about exactly this scope problem. Prefer a certificate per hostname — ACME makes issuing many of them free and automatic, which removes the operational reason wildcards existed.

Standards and references

Test this on your domain

Run the check that produces this finding, on its own, against any domain.

Open the tls certificate checkerBuild the fix

Other tls certificate checks