CVE-2023-43809: Soft Serve Public Key Authentication Bypass Vulnerability when Keyboard-Interactive SSH Authentication is Enabled

Vulnerability summary

CVE-2023-43809 is a high (CVSS 7.5) Improper Authentication vulnerability in charm soft_serve. EPSS estimates a 1.22% chance of exploitation in the next 30 days, higher than 68.6% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 04-10-2023
   PublishedVulnerability first disclosed.
2. 20-09-2024
   Last modifiedVulnerability information updated.

Description

Soft Serve is a self-hostable Git server for the command line. Prior to version 0.6.2, a security vulnerability in Soft Serve could allow an unauthenticated, remote attacker to bypass public key authentication when keyboard-interactive SSH authentication is active, through the `allow-keyless` setting, and the public key requires additional client-side verification for example using FIDO2 or GPG. This is due to insufficient validation procedures of the public key step during SSH request handshake, granting unauthorized access if the keyboard-interaction mode is utilized. An attacker could exploit this vulnerability by presenting manipulated SSH requests using keyboard-interactive authentication mode. This could potentially result in unauthorized access to the Soft Serve. Users should upgrade to the latest Soft Serve version `v0.6.2` to receive the patch for this issue. To workaround this vulnerability without upgrading, users can temporarily disable Keyboard-Interactive SSH Authentication using the `allow-keyless` setting.

• CWE-287Improper AuthenticationWhen an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.