shadow1ng/fscan · warning

redis_ping_failed

Error message

redis_ping_failed

What it means

After connecting and authenticating the handshake to a Redis server, the plugin sends a PING and expects a reply containing "PONG". If the raw response bytes do not contain PONG, it closes the connection and fails the auth attempt with redis_ping_failed, embedding the actual response text via i18n.Tr. This guards against servers that accept TCP on 6379 but do not speak RESP correctly (proxies, honeypots, HTTP endpoints, or a server requiring AUTH that returns an error string instead of PONG).

Solutions

1. Check the actual response text embedded in the error to see what the server returned.
2. If it is -NOAUTH, provide correct Redis credentials before the PING (set the password in the auth config).
3. Verify the target is really Redis: run redis-cli -h <host> -p <port> PING manually.
4. Confirm protected-mode is disabled or the scanner source IP is allowed (bind/ACL settings in redis.conf).

Example fix

// before (server returns -NOAUTH)
conn.Write([]byte("PING\r\n")) // -> "-NOAUTH Authentication required."
// after
conn.Write([]byte("AUTH mypassword\r\n"))
conn.Write([]byte("PING\r\n")) // -> "+PONG"

conn, err := net.DialTimeout("tcp", host+":6379", 3*time.Second)
if err == nil {
    fmt.Fprintf(conn, "PING\r\n")
    buf := make([]byte, 64)
    n, _ := conn.Read(buf)
    if !strings.Contains(string(buf[:n]), "PONG") { /* expect redis_ping_failed; inspect raw response */ }
    conn.Close()
}

func isPong(resp string) bool { return strings.Contains(resp, "PONG") }

res, err := plugin.Scan(ctx, target)
if err != nil {
    var ae *AuthResult
    if strings.Contains(err.Error(), "-NOAUTH") {
        // supply credentials and retry
    } else {
        log.Printf("redis probe not a real Redis server: %v", err)
    }
}

When it happens

Trigger: doRedisAuth connects to a Redis port, completes its handshake, sends PING, and the response string does not contain "PONG" — e.g. the server returned "-NOAUTH Authentication required", "-ERR unknown command", an HTTP error page, or garbage bytes.

Common situations: Redis protected-mode or ACLs rejecting unauthenticated PING; the port actually hosts a different service (memcached, an HTTP proxy, a honeypot); a RESP-incompatible middleware in front of Redis; scanning a non-Redis service that happens to listen on 6379.

Understand the failure class

Background: "invalid response format", "malformed payload", "missing data field": when an API returns 200 but the response shape is wrong — this error's family across 23 libraries.

Related errors

• accept status
• activemq_stomp_read_failed
• activemq_stomp_send_failed
• authentication failed
• cannot find DC for

AI-assisted analysis of shadow1ng/fscan@95cc12e753 (2026-09-06). Data as JSON: /api/errors/06bb0808699e46a3. Report an issue: GitHub.

Appendix: source

Thrown at plugins/services/redis.go:173

	_ = conn.SetReadDeadline(time.Now().Add(timeout))
	response := make([]byte, 512)
	n, pingReadErr := conn.Read(response)
	if pingReadErr != nil {
		_ = conn.Close()
		return &AuthResult{
			Success:   false,
			ErrorType: ErrorTypeNetwork,
			Error:     pingReadErr,
		}
	}

	responseStr := string(response[:n])
	if !strings.Contains(responseStr, "PONG") {
		_ = conn.Close()
		return &AuthResult{
			Success:   false,
			ErrorType: ErrorTypeUnknown,
			Error:     fmt.Errorf("%s", i18n.Tr("redis_ping_failed", strings.TrimSpace(responseStr))),
		}
	}

	return &AuthResult{
		Success:   true,
		Conn:      conn,
		ErrorType: ErrorTypeUnknown,
		Error:     nil,
	}
}

// classifyRedisErrorType Redis错误分类
func classifyRedisErrorType(err error) ErrorType {
	if err == nil {
		return ErrorTypeUnknown
	}

	redisAuthErrors := []string{

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