Beszel is a server monitoring platform. Prior to version 0.18.2 its authenticated API endpoints pass the user‑supplied "container" query parameter to the agent without validation. Because the agent uses the raw value when forming Docker Engine API URLs, an authenticated user—including those with a read‑only role—can inject "../" sequences to traverse to arbitrary Docker API endpoints on the agent host. This path traversal flaw (CWE‑22) allows an attacker to access sensitive infrastructure details, such as container configurations and logs, and potentially perform actions exposed by the Docker API.

The vulnerability affects the Beszel platform released by henrygd. All releases earlier than 0.18.2 are impacted; the issue was fixed in 0.18.4. Administrators should confirm that their deployments are running a patched version.

The CVSS score is 6.5 and the EPSS indicates a very low exploitation probability (<1%), and the issue is not listed in the CISA KEV catalog. Exploitation requires an authenticated session to Beszel, after which the attacker can issue arbitrary Docker Engine commands through the agent. While the current threat of exploitation is low, the impact on confidentiality is substantial, warranting prompt remediation.