CVE-2026-43921
CVE-2026-43921 is a high-severity vulnerability with a CVSS 4.0 base score of 8.9. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-94.
Key facts
- Severity: High (CVSS 4.0 base score 8.9)
- EPSS exploit prediction: 0% (19th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-94
- Published:
- Last modified:
Description
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.
Frequently asked questions
- What is CVE-2026-43921?
- 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.
- How severe is CVE-2026-43921?
- CVE-2026-43921 has a CVSS 4.0 base score of 8.9, rated high severity.
- Is CVE-2026-43921 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (19th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-43921?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- When was CVE-2026-43921 published?
- CVE-2026-43921 was published on 2026-07-06 and last updated on 2026-07-07.
References
Other CWE-94 (Code Injection) vulnerabilities
- CVE-2026-57624 — Critical (CVSS 10.0): Unauthenticated Remote Code Execution (RCE) in Blocksy Companion Pro <= 2.1.46 versions.
- CVE-2026-10134 — Critical (CVSS 10.0): IBM Langflow OSS 1.0.0 through 1.9.3 allows an attacker to read every secret available to the Langflow process, read…
- CVE-2026-53576 — Critical (CVSS 10.0): Kestra is an open-source, event-driven orchestration platform. Prior to 1.0.45 and 1.3.21, the authentication filter…
- CVE-2026-10561 — Critical (CVSS 10.0): IBM Langflow OSS 1.0.0 through 1.9.3 has an vulnerability due to an improper isolation of Python execution combined…
- CVE-2026-25470 — Critical (CVSS 10.0): Improper Control of Generation of Code ('Code Injection') vulnerability in ACPT ACPT (Pro) - Custom Post Types Plugin…
- CVE-2026-48836 — Critical (CVSS 10.0): Unauthenticated Remote Code Execution (RCE) in Easy Invoice <= 2.1.19 versions.