PCI Compliance failed UDP port 500


Hello Everyone,

I have a customer that has a Peplink Balance One running FW 7.1.0 Build 3433. Just recently they started failing PCI compliance and the results were stating because UDP port 500 was open relating to remote desktop. After taking a look I showed that I had remote user access turned on using L2TP with IPsec. I turned it off and the PCI scan then started passing. However, the user needs this remote user access turned on to get access to the network remotely. Is there by chance an updated firmware that fixes this issue?


Hello jondjr,

UDP 500 and 4500 are common port when IPsec is being used. This port being open is expected.


Thanks for this response. It is helpful.

I want to add on to this that I also received this PCI fail for the same reason, but I received a couple related fail notices that you might want to be aware of for other customers:

  1. “Weak encryption ciphers, such as DES or 3DES, were identified as supported on this VPN device. These weak ciphers could make it easier for a context dependent attack to compromise the integrity of IKE sessions established with this device.”

  2. “Diffie-Hellman Groups 1 to 4 are no longer considered safe for strong encryption. It is estimated that these groups have a security level of 80-90 bits which is no longer adequate to protect the encryption keys used during IKE phase 2. Furthermore, Group 5 (Modp-1536) has a security level of 120 bits which is slightly under to protect AES-128 encryption keys. Stronger groups have been designed for the Diffie-Hellman key exchange in RFC 3526.”


Here’s another fail for the updated PCI scan:

  1. SSL Certificate is Not
    Trusted (External Scan)
    Port: tcp/32015
    It was not possible to validate the SSL certificate, and thus it could not
    be trusted. Users may receive a security warning when using this
    service. This occurs because either the certificate or a certificate in its
    chain has issues that prevent validation. Some examples of these
    issues are, but not limited to, a certificate having expired, the
    hostname does not have match the name on the certificate, or the
    certificate is not signed by a well-known Certificate Authority (CA).
    CVSSv2: AV:N/AC:M/Au:N/C:P/I:P/A:P
    Service: generic_ssl
    Subject: /OU=Domain Control Validated/OU=PositiveSSL/CN=captiveportal.
    Issuer: /C=GB/ST=Greater Manchester/L=Salford/O=COMODO CA
    Limited/CN=COMODO RSA Domain Validation Secure Server CA
    Certificate Chain Depth: 0
    Reason: The hostname on the certificate does not match any of the
    hostnames provided to the scanner.

The issue I have here is that I have captive portal disabled on this device, so how the external scan is even picking up the captiveportal.peplink.com is confusing to me. Can anyone help me understand how this would be happening?


And one more that is lower priority concern:

  1. System Responds to SYN+FIN TCP Packets. Port: tcp/10
    This device responded to a TCP packet with both the SYN and FIN bits
    set. Such packets do not occur in typical network traffic, but can be
    used by attackers to bypass the security rules configured in nonstateful
    firewalls and establish connections with protected hosts.
    CVSSv2: AV:N/AC:L/Au:N/C:N/I:N/A:N
    Service: generic_tcp
    Verify that stateful inspection has been implemented on the network to
    protect this host from out-of-state attacks. Confirm with your vendor
    that there are no known rule-bypass concerns with this device, and
    that the software revision is current. You may additionally wish to
    create specific filtering rules designed to drop or reject packets with
    certain combinations of bits set in initial synchronization packets such
    as SYN/FIN, and SYN/RST. Do not use routable IP space internally,
    except within your DMZ.



Let us start discuss the PCI compliance by referring to the PCI compliance guide below:

Some of the settings you need to enable (as shown in the guide) before you start the scanning.

The above certificate is the default certificate for the device, you can upload your own cert to make sure the certificate used is compliance. Please refer to the screenshot below:

For the above, may i know how the PCI scanning is performed ? Do you scan directly connect to the WAN port for the Balance One ?


For #3, I’m still confused why an external WAN PCI scan would discover the captiveportal.peplink.com certificate when the captive portal feature is disabled on this device.

When VPN IPSEC is enabled, the PCI scan also finds the same certificate error. However, when VPN is disabled, the PCI scan does not find the certificate error. To me, both VPN and captiveportal would behave the same for these scans. If enabled, the scanner would see the generic certificates and give the error. If not enabled, the scanner shouldn’t give the error.

Re: 4. It is done by an external 3rd party. Trustwave. Edit: They scan our IP addresses connected to the Peplink device. There is no on-site testing.


If the captive portal is disabled, the PCI scan shouldn’t be detecting any issues. Are you managing the Balance One from IC2?


I’m managing the Balance One directly from the device.

I took a closer look, and the “default certificate” for web admin uses the same captiveportal.peplink.com certificate name. I think that is why it appeared to be the captiveportal showing up/being scanned. I thought the certs were different for each service.

The 32015 port is related to speedfusion and PepVPN handshake port, and we are using PepVPN.



Yes, that is what i trying to explain here.