Description

froxlor versions before 2.2.5 fail to validate newline characters in subdomain redirect URLs, allowing authenticated customers to inject arbitrary nginx or Apache configuration directives. Attackers can supply URLs containing literal newlines that are written verbatim into vhost config files during cron rebuild, enabling web server configuration corruption, denial of service, or hijacking of HTTP responses across hosted domains.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.9",
  "pubDate": "2026-09-14T13:19:32.277Z",
  "pubdate": "2026-09-14T13:19:32.277Z",
  "executiveSummary": "Froxlor versions prior to 2.2.5 contain a critical vulnerability involving improper validation of input used in subdomain redirect URLs.\nThis flaw enables authenticated customers to perform configuration injection attacks against Nginx or Apache web server software.\nBy injecting newline characters into the redirect URL field, an attacker can manipulate the generated virtual host (vhost) configuration files.\nThe vulnerability poses a severe risk to multi-tenant environments, as successful exploitation allows for unauthorized modification of server-side directives.\nAttacker capabilities include disrupting server operations, causing denial of service (DoS), or performing HTTP response hijacking across hosted domains.\nExploitation requires authenticated access to the Froxlor customer interface, limiting the attack surface to registered users with standard privilege levels.\nThe primary risk implication is the compromise of the integrity of the web server configuration, which is managed by the application's automated cron-based rebuild process.",
  "technicalDetails": "The vulnerability resides in the input validation logic for subdomain redirect URLs within the Froxlor management panel. The application fails to sanitize or neutralize newline characters (CR/LF) before committing these values to the underlying system configuration data structures.\nIn the Froxlor architecture, configuration files for web servers such as Nginx and Apache are dynamically generated based on values stored in the database. These files are updated periodically via a cron job that executes a configuration rebuild process.\nThe exploitation flow begins with an authenticated customer navigating to the subdomain management interface. By inputting a crafted URL string containing injected newline characters followed by arbitrary server configuration directives (e.g., 'proxy_pass', 'alias', or 'rewrite' rules), the attacker manipulates the internal data set.\nDuring the next scheduled execution of the configuration rebuild task, the application writes the malicious input verbatim into the vhost configuration file. Because the web server process subsequently reloads these configuration files, the injected directives are parsed and executed by the web server.\nThis injection allows for significant administrative control over the HTTP request/response pipeline. For instance, an attacker could force the server to redirect traffic to an arbitrary destination, disclose internal file paths, or bypass security headers applied to other virtual hosts on the same server.\nThe vulnerability is present in all versions of Froxlor prior to 2.2.5. The root cause is the reliance on user-provided input without enforcing a strict allowlist or character filtering mechanism, specifically failing to detect and reject control characters that act as delimiters in configuration syntax.\nPost-exploitation, the attacker maintains influence over the server's behavior until the malicious configuration is manually removed or overwritten. Since the configuration file acts as the source of truth for the web server, the impact is persistent across application restarts and service reloads. The lack of input validation at the application layer translates directly into unauthorized configuration file tampering, demonstrating a breakdown in the secure bridge between the web interface and the underlying infrastructure management service."
}