CVE-2026-43921 HIGH

CVE-2026-43921: FOSSBilling vulnerable to arbitrary PHP code injection via unescaped config serialization

Vendor Fossbilling
Product FOSSBilling
Weakness CWE-94 · Code injection
Published July 6, 2026
Last update July 6, 2026

CVSS base score

8.9/10
Attack vector Network
Attack complexity Low
Privileges required High
User interaction None
Confidentiality
Integrity

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

What the vulnerability does

01Description

FOSSBilling is a free, open-source billing and client management system. Versions 0.6.10 through 0.7.2 have a PHP code injection vulnerability in FOSSBilling's `Config::prettyPrintArrayToPHP()` method. When configuration values are updated, string values are written into `config.php` without escaping single quotes. Because `config.php` is loaded via a bare `include` on every HTTP request, an attacker with admin privileges can inject arbitrary PHP code that executes on every subsequent request. Version 0.8.0 contains a patch. Some workarounds are available. Restrict admin access to trusted personnel only; audit `config.php` for unexpected PHP code; and/ or at the reverse proxy/WAF level, restrict access to admin API endpoints that modify configuration.

Key dates

02Disclosure timeline

July 6, 2026 CVE published

Related vulnerabilities

04Related CVE