Executive brief
froxlor is a hosting control panel used by ISPs and hosting providers to manage customer domains and web servers. A vulnerability in how it processes subdomain redirect URLs allows authenticated customers to inject malicious configuration directives into nginx or Apache web server config files, potentially corrupting the entire server configuration, causing outages for all hosted customers, or hijacking web traffic for other domains on the same server.
Technical details
froxlor contains a CRLF injection vulnerability (CWE-93) in the subdomain management API and UI. When customers create or update a subdomain redirect, the redirect URL is validated only for correct scheme and hostname, but the path component is not checked for newline characters (0x0A). The unvalidated URL is later written verbatim into nginx and Apache vhost configuration files during the cron rebuild cycle. An authenticated customer with subdomain modification rights can supply a URL containing literal newlines (e.g., http://attacker.com/path%0Ainjected_config) to break out of the current configuration directive and inject arbitrary nginx or Apache directives. This enables configuration corruption, denial of service by introducing syntax errors, hijacking of HTTP responses across other domains, and potential exposure of sensitive files via nginx include directives. Patches are available in version 2.2.5 and later.
Affected products
- froxlor froxlor before 2.2.5
Timeline
- 2026-06-29: disclosed
- 2026-09-14: advisory