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

Vulnerability summary

CVE-2026-27734 is a medium (CVSS 6.5) vulnerability in beszel. EPSS estimates a 0.55% chance of exploitation in the next 30 days, higher than 45.7% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 27-02-2026
   PublishedVulnerability first disclosed.
2. 02-03-2026
   Last modifiedVulnerability information updated.

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.

• CWE-22Improper Limitation of a Pathname to a Restricted DirectoryThe product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.