henrygd beszel up to 0.18.6 API Endpoint incomplete blacklist

Summaryinfo

A vulnerability was found in henrygd beszel up to 0.18.6. It has been rated as critical. The impacted element is an unknown function of the component API Endpoint. This manipulation causes incomplete blacklist. This vulnerability is handled as CVE-2026-40077. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability classified as problematic was found in henrygd beszel up to 0.18.6. Affected by this vulnerability is an unknown function of the component API Endpoint. The manipulation with an unknown input leads to a incomplete blacklist vulnerability. The CWE definition for the vulnerability is CWE-184. The 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, leading to resultant weaknesses. As an impact it is known to affect confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-40077 since 04/09/2026. The exploitation appears to be difficult. The attack can be launched remotely. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1562.006 according to MITRE ATT&CK.

Upgrading to version 0.18.7 eliminates this vulnerability.

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Productinfo

Vendor

• henrygd

Name

• beszel

Version

• 0.18.0
• 0.18.1
• 0.18.2
• 0.18.3
• 0.18.4
• 0.18.5
• 0.18.6

Website

• Product: https://github.com/henrygd/beszel/

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