Sysax Multi-Server Denial-of-Service Vulnerability in SSH Daemon

A denial-of-service vulnerability has been identified in Sysax Multi-Server version 6.10, specifically within its SSH daemon. The issue arises when the server processes malformed key exchange packets, including a non-standard byte in place of the expected SSH protocol delimiter. This exploitation leads to a crash in the service, causing a loss of availability.

Impact

Exploitation of this vulnerability causes the SSH service to crash, leading to a denial-of-service condition where the service becomes unavailable.

Reproduction

The vulnerability can be reproduced by sending a specially crafted SSH key exchange packet that includes a non-standard byte in place of the expected delimiter. This can be done using the Metasploit module 'sysax_sshd_kexchange.rb', which automates the process of sending the malformed packet and causing the service to crash.

Remediation

Users are advised to update to Sysax Multi-Server version 6.11, which addresses this vulnerability. The updated version is available on the Sysax website.