topic Re: Insecurity message with ssh in switch 3850 in Network Security

Insecurity message with ssh in switch 3850

Leftz — Tue, 01 Feb 2022 16:55:07 GMT

Hi We have switch c3850/ver 03.03.01.SE. Now some insecurity message (Please see the below) is sent to us from tenable.

The device has the below two commands. Are these two commands is the reason for the insecurity? Thank you

ip ssh server algorithm encryption aes128-ctr aes192-ctr aes256-ctr
ip ssh client algorithm encryption aes128-ctr aes192-ctr aes256-ctr

-------

message is from tenable:

"The remote service accepts connections encrypted using SSL 2.0 and/or
SSL 3.0. These versions of SSL are affected by several cryptographic
flaws, including:

- An insecure padding scheme with CBC ciphers.

- Insecure session renegotiation and resumption schemes.

An attacker can exploit these flaws to conduct man-in-the-middle
attacks or to decrypt communications between the affected service and
clients.

Although SSL/TLS has a secure means for choosing the highest supported
version of the protocol (so that these versions will be used only if
the client or server support nothing better), many web browsers
implement this in an unsafe way that allows an attacker to downgrade
a connection (such as in POODLE). Therefore, it is recommended that
these protocols be disabled entirely.

NIST has determined that SSL 3.0 is no longer acceptable for secure
communications. As of the date of enforcement found in PCI DSS v3.1,
any version of SSL will not meet the PCI SSC's definition of 'strong
cryptography'."

Re: Insecurity message with ssh in switch 3850

Rob Ingram — Tue, 01 Feb 2022 17:00:16 GMT

@Leftz that message from tenable is probably referring to the https server that is enabled on the switch, not ssh.

If you are not using it you can disable using "no ip http secure-server" you can also disable http server "no ip http server".

Re: Insecurity message with ssh in switch 3850

Leftz — Tue, 01 Feb 2022 17:22:58 GMT

Hi Rob, Thank you very much! I think you are right.

Re: Insecurity message with ssh in switch 3850

Leo Laohoo — Tue, 01 Feb 2022 22:59:19 GMT

@Leftz wrote:

We have switch c3850/ver 03.03.01.SE.

If the switch's firmware cannot/will-not be upgraded, anything else is an exercise of futility.

Re: Insecurity message with ssh in switch 3850

Leftz — Wed, 02 Feb 2022 16:26:01 GMT

Thank you Leo!