CVE-2026-28496 json
FOSSBilling: Server-side template injection in Twig template rendering enables information disclosure and RCE
published 2026-06-23 4 mo ago modified 2026-06-23 4 mo ago also EUVD-2026-38455
- cvss
- 9.4
- version 4.0, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 1.9%
- EPSS 1.9% chance of exploitation in 30 days, percentile 79%
- public exploits
- 0
- none known, plus a Nuclei check
Summary
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.
Patch / fix
- fossbilling fossbilling 0.8.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
- Assessed
- 4 mo ago
Exploit prediction
1.91% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- Nuclei template FOSSBilling - Server-Side Template Injection nuclei detection template
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 9.4 | CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H |
| CNA | 4.0 | 9.4 | CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
Affected products
- FOSSBilling FOSSBilling
Classification
- Weakness
-
- CWE-1336 Improper Neutralization of Special Elements Used in a Template Engine
References
Sources
- CVE List CVE-2026-28496
- NVD CVE-2026-28496
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.