CVE-2025-40927

CGI::Simple versions before 1.282 for Perl has a HTTP response splitting flaw

This vulnerability is a confirmed HTTP response splitting flaw in CGI::Simple that allows HTTP response header injection, which can be used for reflected XSS or open redirect under certain conditions.

Although some validation exists, it can be bypassed using URL-encoded values, allowing an attacker to inject untrusted content into the response via query parameters.

As a result, an attacker can inject a line break (e.g. %0A) into the parameter value, causing the server to split the HTTP response and inject arbitrary headers or even an HTML/JavaScript body, leading to reflected cross-site scripting (XSS), open redirect or other attacks.

The issue documented in CVE-2010-4410 https://www.cve.org/CVERecord?id=CVE-2010-4410 is related but the fix was incomplete.

Impact

By injecting %0A (newline) into a query string parameter, an attacker can:

* Break the current HTTP header

* Inject a new header or entire body

* Deliver a script payload that is reflected in the server’s response

That can lead to the following attacks:

* reflected XSS

* open redirect

* cache poisoning

* header manipulation