grafana/k6 · error

unknown cipher suite id '%d'

Error message

unknown cipher suite id '%d'

What it means

Raised by TLSCipherSuites.MarshalJSON when serializing the configured cipher list: a numeric cipher suite ID in the options has no entry in SupportedTLSCipherSuitesToString, so it cannot be rendered as a name. Typically the result of programmatically set or stale options containing an unknown suite constant.

Source

Thrown at lib/options.go:91

		fields.Min = ver
		fields.Max = ver
	}
	*v = TLSVersions(fields)
	return nil
}

// TLSCipherSuites represents a list of TLS cipher suites.
// Marshals and unmarshals from a list of names, eg. "TLS_ECDHE_RSA_WITH_RC4_128_SHA".
type TLSCipherSuites []uint16

// MarshalJSON will return the JSON representation according to supported TLS cipher suites
func (s *TLSCipherSuites) MarshalJSON() ([]byte, error) {
	var suiteNames []string
	for _, id := range *s {
		if suiteName, ok := SupportedTLSCipherSuitesToString[id]; ok {
			suiteNames = append(suiteNames, suiteName)
		} else {
			return nil, fmt.Errorf("unknown cipher suite id '%d'", id)
		}
	}

	return json.Marshal(suiteNames)
}

// UnmarshalJSON implements the json.Unmarshaler interface
func (s *TLSCipherSuites) UnmarshalJSON(data []byte) error {
	var suiteNames []string
	if err := StrictJSONUnmarshal(data, &suiteNames); err != nil {
		return err
	}

	var suiteIDs []uint16
	for _, name := range suiteNames {
		if suiteID, ok := SupportedTLSCipherSuites[name]; ok {
			suiteIDs = append(suiteIDs, suiteID)
		} else {

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Use only cipher suite names from Go's crypto/tls supported list (e.g. TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256)
2. Avoid injecting raw numeric cipher IDs into options

When it happens

Trigger: Thrown at lib/options.go:91 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/77caa8b8cd2ccc6f. Report an issue: GitHub.