CVE-2026-40077: Beszel has an IDOR in hub API endpoints that read system ID from URL parameter

Vulnerability summary

CVE-2026-40077 is a low (CVSS 3.5) Incomplete List of Disallowed Inputs vulnerability in beszel. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12.5% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 09-04-2026
   PublishedVulnerability first disclosed.
2. 13-04-2026
   Last modifiedVulnerability information updated.

Description

Beszel is a server monitoring platform. Prior to 0.18.7, some API endpoints in the Beszel hub accept a user-supplied system ID and proceed without further checks that the user should have access to that system. As a result, any authenticated user can access these routes for any system if they know the system's ID. System IDs are random 15 character alphanumeric strings, and are not exposed to all users. However, it is theoretically possible for an authenticated user to enumerate a valid system ID via web API. To use the containers endpoints, the user would also need to enumerate a container ID, which is 12 digit hexadecimal string. This vulnerability is fixed in 0.18.7.

• CWE-184Incomplete List of Disallowed InputsThe product implements a protection mechanism that relies on a list of inputs (or properties of inputs) that are not allowed by policy or otherwise require other action to neutralize before additional processing takes place, but the list is incomplete.