CVE-2026-28496
Published: 23 June 2026
Summary
CVE-2026-28496 is a critical-severity Improper Neutralization of Special Elements Used in a Template Engine (CWE-1336) vulnerability. Its CVSS base score is 9.4 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 23.0% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-38455
Vulnerability details
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,…
more
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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
SSTI in public-facing billing app directly enables exploitation for RCE via command interpreters.
Affected Assets
Mitigating Controls
No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.