SSH vulnerabilities: HMAC algorithms and CBC ciphers

Solution Verified - Updated -


  • As per NCircle, the following vulnerabilities were received on RHEL 5 and RHEL 6 servers:
SSH Insecure HMAC Algorithms Enabled
SSH CBC Mode Ciphers Enabled

Below is the update from NCircle regarding the vulnerabilities 

Vulnerability Name: SSH Insecure HMAC Algorithms Enabled

Description: Insecure HMAC Algorithms are enabled

Disable any 96-bit HMAC Algorithms.Disable any MD5-based HMAC Algorithms.
Vulnerability Name: SSH CBC Mode Ciphers Enabled

Description: CBC Mode Ciphers are enabled on the SSH Server.

Solution: Disable CBC Mode Ciphers and use CTR Mode Ciphers


  • Red Hat Enterprise Linux 5
  • Red Hat Enterprise Linux 6
  • SSH
  • Putty

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