Cisco ASA – Disable SSLv3 (Force TLSv1.0) – Mitigate POODLE

KB ID 0001052


Eliminate Poodle

By default the Cisco ASA will allow connection via SSLv3. The POODLE exploit works by forcing SSL to fall back to SSLv3 and then decrypting that communication. However you are still not completely protected as per this Threat Validation, so the ASA platform can still be attacked via TLSv1.0. Note: At time of writing TLSv1.2 is not supported, but it is on the road-map for version 9.3(2).

So this procedure will not completely eliminate the threat, but it’s as mitigated as it’s possible to be at this time, (And TLSv1 is considered more secure than SSLv3 anyway).


1. You can check your firewall is contactable via SSLv3, here I’m on MAC OSX and I’ve got OpenSSL installed. If I try to initiate an SSLv3 connection it works.

openssl s_client -connect {IP_or_Hostname} -ssl3

OpenSSL Text for SSLv3

Or if you have nmap installed you can use that as well;

nmap –script ssl-enum-ciphers {IP_of_Hostname}


2. Below you can see I’m confirming the SSL settings (i.e. it will accept SSLv3). Then I force the firewall to only accept TLSv1.0.

Petes-ASA# configure terminal
Petes-ASA(config)# ssl client-version tlsv1-only 
Petes-ASA(config)# ssl server-version tlsv1-only 

You can see, afterwards when I view the SSL options, only TLSv1 will be accepted.

ASA 5500 Disable SSLv3

3. If you prefer to use the ADSM, then you will find the same settings at, Configuration > Remote Access VPN > Advanced > SSL Settings;

The SSL version for the security appliance to negotiate as a ‘server’ = TLS V1 Only

The SSL version for the security appliance to negotiate as a ‘client’ = TLS V1 Only

ASA ASDM Disable SSLv3


4. Don’t forget to ‘Apply’ and then save the changes.

Cisco ASA Testing for SSLv3

Simply perform the tests that I did above;

1. Proving the absence of SSLv3 with OpenSSL.


2. Proving the absence of SSLv3 with nmap.

Eliminate Poodle

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Author: Migrated

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