GHSA-4g76-w3xw-2x6w is a critical-severity (CVSS 9.1) Improper Authentication vulnerability in github.com/foxcpp/maddy. O3 Security confirms whether GHSA-4g76-w3xw-2x6w is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Full authentication bypass if SASL authorization username is specified
Real-World Exposure
github.com/foxcpp/maddyReal-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
Impact
maddy 0.2.0 - 0.6.2 allows a full authentication bypass if SASL authorization username is specified when using the PLAIN authentication mechanisms. Instead of validating the specified authorization username, it is accepted as is after checking the credentials for the authentication username.
Patches
maddy 0.6.3 includes the fix for the bug.
Workarounds
There is no way to fix the issue without upgrading.
References
- Commit that introduced the vulnerable code: https://github.com/foxcpp/maddy/commit/55a91a37b71210f34f98f4d327c30308fe24399a
- Fix: https://github.com/foxcpp/maddy/commit/9f58cb64b39cdc01928ec463bdb198c4c2313a9c
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/foxcpp/maddy | ≥ 0.2.0&&< 0.6.3 | 0.6.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/foxcpp/maddy. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/foxcpp/maddy to 0.6.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4g76-w3xw-2x6w is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-4g76-w3xw-2x6w is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-4g76-w3xw-2x6w. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-4g76-w3xw-2x6w in your dependencies?
O3 detects GHSA-4g76-w3xw-2x6w across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.