CVE-2025-13434: Jameschz Hush Framework RCE Vulnerability

CVE-2025-13434 Overview

A HTTP Host Header Injection vulnerability has been identified in Jameschz Hush Framework 2.0. The vulnerability exists within an unknown function in the file Hush\hush-lib\hush\Util.php of the HTTP Host Header Handler component. Through manipulation of the $_SERVER['HOST'] argument, an attacker can achieve improper neutralization of HTTP headers for scripting syntax, potentially enabling HTTP response splitting attacks.

Critical Impact

Remote attackers can exploit this vulnerability to inject malicious content into HTTP headers, potentially leading to cache poisoning, cross-site scripting, or session manipulation attacks.

Affected Products

• Jameschz Hush Framework 2.0
• Applications built on Hush Framework utilizing the HTTP Host Header Handler component
• Systems running the vulnerable Util.php component

Discovery Timeline

• 2025-11-20 - CVE-2025-13434 published to NVD
• 2025-12-11 - Last updated in NVD database

Technical Details for CVE-2025-13434

Vulnerability Analysis

This vulnerability stems from improper handling of the HTTP Host header within the Hush Framework's utility component. The framework fails to properly sanitize or validate the $_SERVER['HOST'] variable before using it in HTTP response headers, allowing attackers to inject arbitrary content. The weakness is classified under CWE-644 (Improper Neutralization of HTTP Headers for Scripting Syntax), indicating that user-controlled input flows into HTTP headers without adequate sanitization.

The vulnerability can be exploited remotely without authentication, as it targets the HTTP Host header which is typically controllable by the client. While the integrity impact is limited, successful exploitation could enable attackers to manipulate HTTP responses, potentially affecting downstream systems or users.

Root Cause

The root cause lies in the Util.php file within the Hush\hush-lib\hush\ directory. The HTTP Host Header Handler component directly processes the $_SERVER['HOST'] value without implementing proper input validation or output encoding. This allows attackers to inject newline characters and additional header content, breaking the intended HTTP response structure.

Attack Vector

The attack is network-based and can be executed remotely. An attacker crafts a malicious HTTP request with a specially constructed Host header containing injected header content or scripting syntax. When the vulnerable Hush Framework processes this request, the malicious content is reflected in the HTTP response headers.

The vulnerability manifests in the Host header handling mechanism within Util.php. An attacker can inject carriage return and line feed characters along with malicious header content into the $_SERVER['HOST'] variable. When the framework generates HTTP responses using this unsanitized value, the injected content becomes part of the response headers. For detailed technical analysis, refer to the GitHub CVE Discovery Document.

Detection Methods for CVE-2025-13434

Indicators of Compromise

• HTTP requests containing unusual characters (CRLF sequences: %0d%0a, \r\n) in the Host header
• Log entries showing malformed or duplicated HTTP headers in responses
• Unexpected cache behavior or cached responses with injected content
• Web application firewall logs indicating header injection attempts

Detection Strategies

• Monitor web server access logs for Host headers containing encoded newline characters or suspicious patterns
• Implement web application firewall rules to detect and block CRLF injection attempts in HTTP headers
• Review application logs for unusual HTTP response anomalies or header manipulation
• Deploy intrusion detection systems with signatures for HTTP header injection attacks

Monitoring Recommendations

• Enable detailed HTTP request logging including full header content
• Configure alerting for requests with abnormally long or malformed Host headers
• Monitor for cache poisoning indicators such as unexpected content variations
• Track any changes to HTTP response headers that deviate from baseline behavior

How to Mitigate CVE-2025-13434

Immediate Actions Required

• Identify all instances of Jameschz Hush Framework 2.0 in your environment
• Implement input validation for the Host header at the web server or reverse proxy level
• Deploy web application firewall rules to filter malicious Host header content
• Consider restricting or validating Host header values against an allowlist of expected hostnames

Patch Information

At the time of disclosure, the vendor (jameschz) was contacted but did not respond. No official patch is currently available for this vulnerability. Organizations using Hush Framework 2.0 should implement workarounds and monitor for any future vendor updates. For additional vulnerability details, consult the VulDB Entry #332978.

Workarounds

• Implement server-level Host header validation to only accept expected domain values
• Use a reverse proxy or web application firewall to sanitize incoming Host headers
• Add custom input sanitization in application code to filter CRLF characters from $_SERVER['HOST']
• Consider migrating to an actively maintained framework if the vendor remains unresponsive

# Apache configuration example - restrict Host header values
# Add to virtual host or .htaccess configuration
RewriteEngine On
RewriteCond %{HTTP_HOST} !^(www\.)?example\.com$ [NC]
RewriteRule ^ - [F]

# Nginx configuration example - validate Host header
# Add to server block
if ($host !~ ^(www\.)?example\.com$) {
    return 444;
}