CVE-2026-28496 Details
Description
FOSSBilling is a free, open-source billing and client management system. Versions prior to 0.8.0 have a Server-Side Template Injection (SSTI) vulnerability in the template rendering system. Administrators with access to features that render Twig templates (email templates, mass mail campaigns, custom payment adapters, and the `string_render` API endpoint) can inject arbitrary Twig expressions, leading to information disclosure and remote code execution. The vulnerability exists because Twig templates are rendered without a sandbox, allowing access to the full Twig environment, API context, and the application's dependency injection container. Version 0.8.0 patches the issue. Some workarounds are available. Audit existing email templates for suspicious Twig expressions, rotate all admin and client API tokens, and/or block external access to /api/system/* at reverse proxy/WAF to mitigate chaining with GHSA-78x5-c8gw-8279.
A server-side template injection (SSTI) vulnerability has been identified in FOSSBilling, a billing and client management system, in versions prior to 0.8.0. This vulnerability allows administrators with access to features that render Twig templates to inject arbitrary Twig expressions. The issue arises because Twig templates are rendered without a sandbox, granting access to the full Twig environment, API context, and the application's dependency injection container. Exploitation of this vulnerability could lead to information disclosure and remote code execution on the host server.
Users are advised to update to FOSSBilling version 0.8.0 or later, where this vulnerability has been patched. Additionally, it is recommended to audit existing email templates for suspicious Twig expressions, rotate all admin and client API tokens, and block external access to '/api/system/*' at the reverse proxy or web application firewall.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Jun 23, 2026CISA-ADP
Assessed Jun 23, 2026References to Advisories, Solutions, and Tools
By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.
| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-57mv-jm88-66jc | [email protected] | AdvisoryBundleRemedyVendor |
| https://github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-78x5-c8gw-8279 | [email protected] | AdvisoryBroken LinkVendor |
| https://www.vulncheck.com/blog/fossbilling-auth-bypass-ssti-rce | [email protected] | BundleExploitRemedyTechnical Analysis |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-1336 | Improper Neutralization of Special Elements Used in a Template Engine | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| FOSSBilling | <= 0.7.2 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 23, 2026 | CVE Modified | CISA-ADP |
| Jun 23, 2026 | New CVE Received | [email protected] |