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Cybersecurity Threat Advisory

In this Cybersecurity Threat Advisory, a critical security flaw in OpenSSH, CVE-2023-38408 has been discovered. This vulnerability could potentially lead to remote code execution in OpenSSH’s forwarded SSH agent, affecting Linux systems and posing a significant threat to organizations’ cybersecurity posture.

What is the threat?

The CVE-2023-38408 vulnerability in OpenSSH allows threat actors to execute remote arbitrary code on Linux systems through the forwarded SSH agent. To exploit this vulnerability, all bad actors need is the existence of specific libraries on the targeted system and forwarding the SSH authentication agent to a system under the attacker’s control. This SSH agent serves as a background utility, securely storing users’ cryptographic keys in memory and enabling seamless remote logins to a server without the need to re-enter passphrases. Attackers can exploit this flaw by sending malicious agent requests to the target system, bypassing authentication measures and gaining unauthorized access. Upon a successful exploitation, attackers can then execute arbitrary commands that can lead to a complete compromise of the affected system, as well as moving laterally across the network.

Why is it noteworthy?

Linux systems are widely used in various organizations, including servers and critical infrastructure. Since OpenSSH is the most, commonly used remote access tool for Linux environments, the flaw poses a significant risk to the confidentiality, integrity, and availability of sensitive data and services. The development of a remote-control execution exploit further escalates the threat, making it crucial for organizations to take immediate action.

What is the exposure or risk?

Organizations using OpenSSH with the Forwarded SSH Agent feature enabled are at significant risk. Attackers exploiting this vulnerability can execute arbitrary code on targeted systems, leading to unauthorized data access, system compromise, and potentially, full control over the affected servers. The risk is particularly high for systems with valuable assets, such as databases, intellectual property, and customer data. Additionally, the potential for lateral movement within an organization’s network raises concerns about the extent of damage an attacker could inflict.

What are the recommendations?

Barracuda MSP recommends the following actions to mitigate the risks posed by this vulnerability:

  • Update OpenSSH: Immediately apply the latest security patches and updates released by the OpenSSH development team to mitigate the vulnerability.
  • Disable SSH Agent Forwarding: If feasible, disable SSH agent forwarding as a temporary measure until the patch can be applied. This can help reduce the attack surface.
  • Access Control: Implement strong access controls and firewall rules to restrict SSH access to trusted IP addresses and networks.


For more in-depth information about the recommendations, please visit the following links:

If you have any questions about this Cybersecurity Threat Advisory, please contact our Security Operations Center.

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Adam Forbes

Posted by Adam Forbes

Adam is a Cybersecurity Analyst at Barracuda MSP. He's a security expert, working on our Blue Team within our Security Operations Center. Adam supports our XDR service delivery and is highly skilled at analyzing security events to detect cyber threats, helping keep our partners and their customers protected.

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