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Ubuntu OS SSH server must be configured to use only FIPS-validated key exchange algorithms.

Overview

Finding IDVersionRule IDIA ControlsSeverity
V-275626RIIM-OS-255060SV-275626r1147928_ruleCCI-000068high
Description
Without cryptographic integrity protections provided by FIPS-validated cryptographic algorithms, information can be viewed and altered by unauthorized users without detection. The system will attempt to use the first algorithm presented by the client that matches the server list. Listing the values "strongest to weakest" is a method to ensure the use of the strongest algorithm available to secure the SSH connection.
STIGDate
Riverbed NetIM OS Security Technical Implementation Guide2025-10-02

Related Frameworks

1 mapping across 4 frameworks
SCF0 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (1) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

NET-14.2Protection of Confidentiality / Integrity Using Encryption
1.00
NIST 800-530 mappings

No source states a mapping between these directly.

Also reachable in 2 hops (33) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

AC-17(1)Monitoring and Control
1.00
AC-17(2)Protection of Confidentiality and Integrity Using Encryption
1.00
AC-3Access Enforcement
1.00
CM-6Configuration Settings
1.00
CM-6(1)Automated Management, Application, and Verification
1.00
CM-7Least Functionality
1.00
CM-7(1)Periodic Review
1.00
IA-2(8)Access to Accounts — Replay Resistant
1.00
IA-2(9)Network Access to Non-privileged Accounts — Replay Resistant
1.00
IA-3Device Identification and Authentication
1.00

+23 more (top 10 by confidence shown)

NIST 800-1710 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (1) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

3.1.13
1.00
CCI1 mapping
CCI-000068
1.00

Details

Check Text (C-275626r1147928_chk)

Verify that the SSH server is configured to use only FIPS-validated key exchange algorithms by using the following command: $ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH 'kexalgorithms' /etc/ssh/sshd_config:KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256 If "KexAlgorithms" does not contain only the algorithms "ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256" in exact order, is commented out, is missing, or conflicting results are returned, this is a finding.

Fix Text (F-79633r1147927_fix)

Configure the SSH server to use only FIPS-validated key exchange algorithms. Add or modify the following line in the "/etc/ssh/sshd_config" file: KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256 Restart the SSH server for changes to take effect: $ sudo systemctl restart sshd.service