Live › vulnerability › CVE-2026-111053
Go to dashboardFOSSBilling's guest template_exists endpoint joins an attacker-supplied file path without stripping traversal sequences, so anyone can probe the server. The endpoint returns only a true or false answer, so an attacker learns whether arbitrary files or directories exist but cannot read their contents.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.
Any self-hosted FOSSBilling installation from 0.1.0 through that exposes its guest API to the internet is exposed, since the endpoint needs no login. Installations that block or restrict the path at the web server or firewall reduce exposure. Teams using a managed FOSSBilling host should confirm the provider has applied the update.
0.8.7api/guestNo product ranges from the sources yet.
0.1.0 through 0.8.7 inclusive.api/guest/system/template_exists containing .. in web server access logs.0.8.7 or later.Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
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.
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