FOSSBilling up to 0.8.6 Path Join template_exists Path::join file path traversal

Summaryinfo

A vulnerability, which was classified as problematic, has been found in FOSSBilling up to 0.8.6. Affected by this issue is the function Path::join of the file /guest/system/template_exists of the component Path Join. The manipulation of the argument File leads to path traversal. This vulnerability is listed as CVE-2026-111053. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in FOSSBilling up to 0.8.6. It has been rated as problematic. This issue affects the function Path::join of the file /guest/system/template_exists of the component Path Join. The manipulation of the argument file with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to CWE-22. The 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. Impacted is confidentiality. The summary by CVE is:

FOSSBilling is an open source billing and client-management platform. From 0.1.0 until 0.8.7, the unauthenticated api/guest/system/template_exists endpoint permits path traversal because templateExists uses Path::join on the attacker-controlled file parameter without rejecting .. sequences or verifying that the resolved path remains inside the active theme directory. The trigger is an unauthenticated request to guest/system/template_exists containing traversal sequences in the file parameter. An attacker can submit traversal sequences in the file parameter and observe the returned boolean to determine whether arbitrary files or directories exist on the server. The oracle does not disclose file contents. This issue is fixed in version 0.8.7.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-111053 since 10/15/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1006 according to MITRE ATT&CK.

Upgrading to version 0.8.7 eliminates this vulnerability.

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Productinfo

Type

• Billing Software

Name

• FOSSBilling

Version

• 0.8.0
• 0.8.1
• 0.8.2
• 0.8.3
• 0.8.4
• 0.8.5
• 0.8.6

Website

• Product: https://github.com/FOSSBilling/FOSSBilling/

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