CVE-2023-43809 : Exploit Details and Defense Strategies

Soft Serve Public Key Authentication Bypass Vulnerability when Keyboard-Interactive SSH Authentication is Enabled

Understanding CVE-2023-43809

Soft Serve, a self-hostable Git server for the command line, was found to have a security vulnerability allowing an attacker to bypass public key authentication when using keyboard-interactive SSH authentication with the

allow-keyless

setting. This could lead to unauthorized access if the keyboard-interaction mode is utilized.

What is CVE-2023-43809?

Prior to version 0.6.2, Soft Serve had a security flaw that could enable an unauthenticated, remote attacker to bypass public key authentication in certain configurations, potentially leading to unauthorized access to the server.

The Impact of CVE-2023-43809

The vulnerability poses a high severity risk as it allows malicious actors to bypass authentication mechanisms and gain unauthorized access to the Soft Serve server, compromising integrity.

Technical Details of CVE-2023-43809

The security vulnerability in Soft Serve pertains to improper authentication (CWE-287) due to insufficient validation procedures during SSH request handshake involving public keys.

Vulnerability Description

The flaw arises from the incorrect validation of public keys when keyboard-interactive SSH authentication is active, allowing attackers to exploit this loophole by presenting manipulated SSH requests, granting unauthorized access.

Affected Systems and Versions

Soft Serve versions prior to

v0.6.2

are affected by this vulnerability, with the potential for exploitation if keyboard-interactive SSH authentication is enabled.

Exploitation Mechanism

Attackers can exploit this vulnerability by leveraging keyboard-interactive authentication mode and manipulating SSH requests to bypass public key authentication.

Mitigation and Prevention

To address CVE-2023-43809, users are advised to take immediate steps and implement long-term security practices.

Immediate Steps to Take

Upgrade to the latest version of Soft Serve

v0.6.2

to receive the necessary patch addressing this vulnerability. Alternatively, users can disable Keyboard-Interactive SSH Authentication using the

allow-keyless

setting.

Long-Term Security Practices

Implement additional client-side verification methods like FIDO2 or GPG to enhance public key validation and strengthen overall authentication procedures.

Patching and Updates

Stay informed about security updates and patches for Soft Serve to address vulnerabilities promptly and ensure a secure environment.