CVE-2023-43809 is a high-severity (CVSS 7.5) Improper Authentication vulnerability in github.com/charmbracelet/soft-serve. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for github.com/charmbracelet/soft-serve — see the affected versions and patch details below.
Soft Serve Public Key Authentication Bypass Vulnerability when Keyboard-Interactive SSH Authentication is Enabled
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-43809.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/charmbracelet/soft-serveReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/charmbracelet/soft-serve | all versions | 0.6.2go get github.com/charmbracelet/soft-serve@v0.6.2 |
Affected Products
soft servecharmResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/charmbracelet/soft-serve, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/charmbracelet/soft-serve to 0.6.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-43809 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2023-43809 in your dependencies?
Find it across Go, including transitive dependencies.