CVE-2024-52875: GFI Kerio Control RCE Vulnerability

CVE-2024-52875 Overview

CVE-2024-52875 is an HTTP Response Splitting vulnerability affecting GFI Kerio Control versions 9.2.5 through 9.4.5. The vulnerability exists in the dest GET parameter passed to multiple unauthenticated pages including /nonauth/addCertException.cs, /nonauth/guestConfirm.cs, and /nonauth/expiration.cs. The parameter is not properly sanitized before being used to generate a Location HTTP header in a 302 HTTP response, enabling attackers to inject arbitrary headers and content.

Critical Impact

This vulnerability chain can escalate from HTTP Response Splitting to Open Redirect, Reflected XSS, and ultimately Remote Command Execution by leveraging the admin interface upgrade feature.

Affected Products

• GFI Kerio Control 9.2.5
• GFI Kerio Control versions through 9.4.5
• All intermediate versions between 9.2.5 and 9.4.5

Discovery Timeline

• 2025-01-31 - CVE-2024-52875 published to NVD
• 2025-09-16 - Last updated in NVD database

Technical Details for CVE-2024-52875

Vulnerability Analysis

This vulnerability is classified under CWE-113 (Improper Neutralization of CRLF Sequences in HTTP Headers), commonly known as HTTP Response Splitting. The flaw occurs when user-controlled input is incorporated into HTTP response headers without proper sanitization of carriage return and line feed (CRLF) characters.

The attack surface is particularly concerning because the vulnerable endpoints are located under the /nonauth/ path, meaning they can be accessed without authentication. An attacker can craft a malicious URL containing CRLF sequences in the dest parameter, which when processed by the server, allows injection of arbitrary HTTP headers and response body content.

The exploitation chain progresses through multiple stages: first, the HTTP Response Splitting enables Open Redirect attacks by manipulating the Location header. Second, by injecting additional response content, attackers can perform Reflected Cross-Site Scripting attacks. Most critically, if an authenticated administrator can be tricked into clicking a malicious link, the XSS payload can interact with the admin interface's upgrade feature, potentially leading to Remote Command Execution on the Kerio Control appliance.

Root Cause

The root cause is insufficient input validation and sanitization in the server-side code handling the dest parameter. The application fails to properly encode or strip CRLF sequences (\r\n or %0d%0a) from user input before incorporating it into the HTTP Location header. This allows attackers to terminate the header section and inject arbitrary content into the HTTP response.

Attack Vector

The attack is network-based and requires user interaction. An attacker must craft a malicious URL targeting one of the vulnerable endpoints and convince a victim to click the link. The unauthenticated nature of the vulnerable pages means no prior access to the system is required.

The exploitation flow involves: crafting a URL with CRLF-encoded sequences in the dest parameter, social engineering a victim (preferably an administrator) to visit the malicious URL, the server generating a 302 redirect response with the injected content, and the victim's browser executing the injected JavaScript. When targeting administrators, the XSS payload can then interact with privileged functionality such as the firmware upgrade feature to achieve code execution.

For detailed technical analysis and proof-of-concept information, see the KarmaInSecurity CVE-2024-52875 Analysis.

Detection Methods for CVE-2024-52875

Indicators of Compromise

• HTTP requests to /nonauth/addCertException.cs, /nonauth/guestConfirm.cs, or /nonauth/expiration.cs containing URL-encoded CRLF sequences (%0d%0a or %0D%0A) in the dest parameter
• Unusual 302 redirect responses with malformed or multiple Location headers
• Web server logs showing requests with encoded newline characters in query parameters
• Evidence of XSS payloads targeting the Kerio Control admin interface

Detection Strategies

• Implement web application firewall rules to detect and block CRLF injection attempts in query parameters
• Monitor HTTP traffic for requests containing %0d, %0a, \r, or \n sequences in the dest parameter
• Configure intrusion detection systems to alert on HTTP Response Splitting patterns targeting the /nonauth/ path
• Review web server access logs for anomalous requests to the three vulnerable endpoints

Monitoring Recommendations

• Enable detailed logging for all requests to /nonauth/ endpoints on Kerio Control appliances
• Implement real-time alerting for requests matching CRLF injection signatures
• Monitor administrator session activity for unexpected interactions with the upgrade functionality
• Track authentication events following visits to unauthenticated endpoints

How to Mitigate CVE-2024-52875

Immediate Actions Required

• Upgrade GFI Kerio Control to a version newer than 9.4.5 that addresses this vulnerability
• If immediate patching is not possible, restrict network access to the Kerio Control web interface
• Educate administrators about the risk of clicking untrusted links while authenticated to the admin interface
• Review logs for evidence of exploitation attempts

Patch Information

Organizations should check with GFI for the latest security updates addressing CVE-2024-52875. For additional details on the vulnerability and remediation, refer to the Full Disclosure Mailing List Post and the KarmaInSecurity CVE-2024-52875 Analysis.

Workarounds

• Implement a reverse proxy or web application firewall in front of Kerio Control to filter CRLF sequences from incoming requests
• Restrict access to the /nonauth/ endpoints using network-level access controls where possible
• Configure browsers used by administrators with enhanced XSS protection and disable JavaScript execution for the Kerio Control domain until patched
• Limit access to the admin interface to specific trusted IP addresses or VPN connections only

# Example WAF rule to block CRLF injection attempts (ModSecurity syntax)
SecRule ARGS:dest "@rx (%0d|%0a|%0D|%0A|\r|\n)" \
    "id:1001,phase:1,deny,status:403,msg:'CRLF Injection Attempt Blocked'"