CVE-2023-43809 Soft Serve Public Key Authentication Bypass Vulnerability when Keyboard-Interactive SSH Authentication is Enabled
Attackers can bypass public key authentication in Soft Serve Git server when keyboard-interactive SSH is enabled, gaining unauthorized access.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2023-43809?
CVE-2023-43809 is a high-severity authentication bypass vulnerability in charmbracelet soft-serve, published on 4 Oct 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-287
Which versions are affected by CVE-2023-43809?
3 open source packages ship an affected version, including github.com/charmbracelet/soft-serve. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/charmbracelet/soft-serve Go | All versions | 0.6.2 |
github.com/charmbracelet/soft-serve Go | All versions | 0.6.2 |
github.com/charmbracelet/soft-serve Go | All versions | 0.6.2 |
Products include Charm Soft Serve.
How do I fix CVE-2023-43809?
Upgrade github.com/charmbracelet/soft-serve to 0.6.2 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2023-43809 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-43809 exists.
Other vulnerabilities in charmbracelet soft-serve
- CVE-2026-30832 Soft Serve: SSRF via unvalidated LFS endpoint in repo import
- CVE-2025-64522 Soft Serve is vulnerable to SSRF through its Webhooks
- CVE-2026-24058 Soft Serve has Critical Authentication Bypass
- CVE-2026-33353 Soft Serve: Authenticated repo import can clone server-local private repositories
- CVE-2026-22253 Soft Serve is missing an authorization check in LFS lock deletion
Sources
Also known as GHSA-mc97-99j4-vm2v, GO-2023-2097.