CVE-2026-40876
CVE-2026-40876 is a security vulnerability in github.com/patrickhener/goshs. O3 Security confirms whether CVE-2026-40876 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
SFTP root escape via prefix-based path validation in goshs
Real-World Exposure
github.com/patrickhener/goshs🐹github.com/patrickhener/goshs/v2Real-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
goshs is a SimpleHTTPServer written in Go. Prior to 2.0.0-beta.6, goshs contains an SFTP root escape caused by prefix-based path validation. An authenticated SFTP user can read from and write to filesystem paths outside the configured SFTP root, which breaks the intended jail boundary and can expose or modify unrelated server files. The SFTP subsystem routes requests through sftpserver/sftpserver.go into DefaultHandler.GetHandler() in sftpserver/handler.go, which forwards file operations into readFile, writeFile, listFile, and cmdFile. All of those sinks rely on sanitizePath() in sftpserver/helper.go. helper.go uses a raw string-prefix comparison, not a directory-boundary check. Because of that, if the configured root is /tmp/goshsroot, then a sibling path such as /tmp/goshsroot_evil/secret.txt incorrectly passes validation since it starts with the same byte prefix. This vulnerability is fixed in 2.0.0-beta.6.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/patrickhener/goshs | all versions | No fix |
| 🐹Go | github.com/patrickhener/goshs/v2 | all versions | 2.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/patrickhener/goshs. 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
No patched version of github.com/patrickhener/goshs has shipped for CVE-2026-40876 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
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 CVE-2026-40876 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 CVE-2026-40876. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-40876 in your dependencies?
O3 detects CVE-2026-40876 across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.