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5.1.19 Ensure sshd MaxSessions is configured

Information

The MaxSessions parameter specifies the maximum number of open sessions permitted from a given connection.

To protect a system from denial of service due to a large number of concurrent sessions, use the rate limiting function of MaxSessions to protect availability of sshd logins and prevent overwhelming the daemon.

Solution

Edit the /etc/ssh/sshd_config file to set the MaxSessions parameter to 10 or less above any Include and Match entries as follows:

MaxSessions 10

Impact:

Limiting MaxSessions caps the number of open sessions (channels) permitted per SSH connection. Users or tools that multiplex many sessions over a single connection may reach the limit and need to open additional connections; set the value in line with site policy.

See Also

https://workbench.cisecurity.org/benchmarks/27890

Item Details

Category: CONFIGURATION MANAGEMENT, IDENTIFICATION AND AUTHENTICATION

References: 800-53|CM-1, 800-53|CM-2, 800-53|CM-6, 800-53|CM-7, 800-53|IA-5

Plugin: Unix

Control ID: af7f6cbd01fd55b2dae77fd946f75b253d370fe16ff2fcaecce16a6fe39ce034