SSH Weak Key Exchange Algorithms Enabled

low Nessus Plugin ID 153953
New! Plugin Severity Now Using CVSS v3

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Synopsis

The remote SSH server is configured to allow weak key exchange algorithms.

Description

The remote SSH server is configured to allow key exchange algorithms which are considered weak.

This is based on the IETF draft document Key Exchange (KEX) Method Updates and Recommendations for Secure Shell (SSH) draft-ietf-curdle-ssh-kex-sha2-20. Section 4 lists guidance on key exchange algorithms that SHOULD NOT and MUST NOT be enabled. This includes:

diffie-hellman-group-exchange-sha1

diffie-hellman-group1-sha1

gss-gex-sha1-*

gss-group1-sha1-*

gss-group14-sha1-*

rsa1024-sha1

Note that this plugin only checks for the options of the SSH server, and it does not check for vulnerable software versions.

Solution

Contact the vendor or consult product documentation to disable the weak algorithms.

See Also

http://www.nessus.org/u?b02d91cd

https://datatracker.ietf.org/doc/html/rfc8732

Plugin Details

Severity: Low

ID: 153953

File Name: ssh_weak_key_exchange_enabled.nasl

Version: 1.2

Type: remote

Family: Misc.

Published: 10/13/2021

Updated: 10/13/2021

Dependencies: ssh_supported_algorithms.nasl

Risk Information

CVSS Score Source: manual

CVSS Score Rationale: Tenable score for weak key exchange

CVSS v2

Risk Factor: Low

Base Score: 2.6

Vector: AV:N/AC:H/Au:N/C:P/I:N/A:N

CVSS v3

Risk Factor: Low

Base Score: 3.7

Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Vulnerability Information