# CVE-2026-40876: SFTP root escape via prefix-based path validation in goshs

> Authenticated SFTP users can escape the configured root directory via prefix-based path validation flaws, allowing unauthorized file access and modification.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 21 Apr 2026
- **Updated:** 22 Apr 2026
- **Also known as:** GHSA-5h6h-7rc9-3824, GO-2026-5146

## What is CVE-2026-40876?

CVE-2026-40876 is a high-severity path traversal vulnerability in patrickhener goshs, published on 21 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official 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.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-40876?

6 open source packages ship an affected version, including github.com/patrickhener/goshs and github.com/patrickhener/goshs/v2. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/patrickhener/goshs` | Go | All versions | None |
| `github.com/patrickhener/goshs` | Go | All versions to 1.1.4 | None |
| `github.com/patrickhener/goshs` | Go | All versions to 1.1.4 | None |
| `github.com/patrickhener/goshs/v2` | Go | All versions | 2.0.0 |
| `github.com/patrickhener/goshs/v2` | Go | All versions | 2.0.0 |
| `github.com/patrickhener/goshs/v2` | Go | All versions | 2.0.0 |

Products: Goshs Goshs.

## How do I fix CVE-2026-40876?

Upgrade to a fixed version.

## Is CVE-2026-40876 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40876 exists.

## Other vulnerabilities in patrickhener goshs

- [CVE-2026-40884](https://insights.sbomify.com/CVE-2026-40884/): goshs: Empty-username SFTP password authentication bypass in goshs (critical 9.8)
- [CVE-2026-35392](https://insights.sbomify.com/CVE-2026-35392/): goshs has an Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in goshs PUT Upload (critical 9.8)
- [CVE-2026-35393](https://insights.sbomify.com/CVE-2026-35393/): Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in goshs POST multipart upload (critical 9.8)
- [CVE-2026-35471](https://insights.sbomify.com/CVE-2026-35471/): Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') in goshs (critical 9.8)
- [CVE-2026-40189](https://insights.sbomify.com/CVE-2026-40189/): goshs has a file-based ACL authorization bypass in goshs state-changing routes (critical 9.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-40876 and fix it if it is affected.

What it is: CVE-2026-40876 is a high-severity path traversal vulnerability in patrickhener goshs, published on 21 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-40876 exists.

Affected packages and fixed versions:
- github.com/patrickhener/goshs (Go): affected all versions; no fix listed
- github.com/patrickhener/goshs (Go): affected all versions up to 1.1.4; no fix listed
- github.com/patrickhener/goshs (Go): affected all versions up to 1.1.4; no fix listed
- github.com/patrickhener/goshs/v2 (Go): affected all versions; fixed in 2.0.0
- github.com/patrickhener/goshs/v2 (Go): affected all versions; fixed in 2.0.0
- github.com/patrickhener/goshs/v2 (Go): affected all versions; fixed in 2.0.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-40876/ (Markdown: https://insights.sbomify.com/CVE-2026-40876/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-40876
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-40876
- OSV: https://osv.dev/vulnerability/CVE-2026-40876

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-40876/
Summaries are generated and may contain mistakes; the official description above is the record.