5.2.11 Ensure only approved MAC algorithms are used

Information

MD5 and 96-bit MAC algorithms are considered weak and have been shown to increase exploitability in SSH downgrade attacks. Weak algorithms continue to have a great deal of attention as a weak spot that can be exploited with expanded computing power. An attacker that breaks the algorithm could take advantage of a MiTM position to decrypt the SSH tunnel and capture credentials and information

Solution

Edit the /etc/ssh/sshd_config file to set the parameter in accordance with site policy. The following includes all supported and accepted MACs: MACs hmac-sha2-512,hmac-sha2-256

See Also

https://workbench.cisecurity.org/files/1859

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-13, CSCv6|3.4

Plugin: Unix

Control ID: e3d1924d33e745a4d5082ffe4365d7f815290a18856d8bda439f1298baf50c22