# CVE-2026-27734: Beszel Vulnerable to Docker API Path Traversal via Unsanitized Container ID

> Authenticated users can traverse Docker API paths to expose sensitive infrastructure details due to unsanitized container IDs.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A: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:** 27 Feb 2026
- **Updated:** 2 Mar 2026
- **Also known as:** GHSA-phwh-4f42-gwf3, GO-2026-4571

## What is CVE-2026-27734?

CVE-2026-27734 is a medium-severity path traversal vulnerability in henrygd beszel, published on 27 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Beszel is a server monitoring platform. Prior to version 0.18.2, the hub's authenticated API endpoints GET /api/beszel/containers/logs and GET /api/beszel/containers/info pass the user-supplied "container" query parameter to the agent without validation. The agent constructs Docker Engine API URLs using fmt.Sprintf with the raw value instead of url.PathEscape(). Since Go's http.Client does not sanitize `../` sequences from URL paths sent over unix sockets, an authenticated user (including readonly role) can traverse to arbitrary Docker API endpoints on agent hosts, exposing sensitive infrastructure details. Version 0.18.4 fixes the issue.

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

## Which versions are affected by CVE-2026-27734?

3 open source packages ship an affected version, including github.com/henrygd/beszel. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/henrygd/beszel` | Go | All versions | 0.18.4 |
| `github.com/henrygd/beszel` | Go | All versions | 0.18.4 |
| `github.com/henrygd/beszel` | Go | All versions | 0.18.4 |

Products: Beszel Beszel.

## How do I fix CVE-2026-27734?

Upgrade github.com/henrygd/beszel to 0.18.4 or later.

## Is CVE-2026-27734 being exploited?

There is no known exploitation of CVE-2026-27734 in the wild and no public exploit code.

## Other vulnerabilities in henrygd beszel

- [CVE-2026-40077](https://insights.sbomify.com/CVE-2026-40077/): Beszel has an IDOR in hub API endpoints that read system ID from URL parameter (low 3.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-27734 and fix it if it is affected.

What it is: CVE-2026-27734 is a medium-severity path traversal vulnerability in henrygd beszel, published on 27 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-27734 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/henrygd/beszel (Go): affected all versions; fixed in 0.18.4
- github.com/henrygd/beszel (Go): affected all versions; fixed in 0.18.4
- github.com/henrygd/beszel (Go): affected all versions; fixed in 0.18.4

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-2026-27734/ (Markdown: https://insights.sbomify.com/CVE-2026-27734/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-27734
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27734
- OSV: https://osv.dev/vulnerability/CVE-2026-27734

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-27734/
Summaries are generated and may contain mistakes; the official description above is the record.