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Critical RCE Flaw in GFI KerioControl Allows Remote Code Execution via CRLF Injection. Threat actors are attempting to exploit a recently disclosed security flaw impacting GFI KerioControl firewalls that, if successfully exploited, could allow malicious actors to achieve remote code execution (RCE). The vulnerability in question, CVE-2024-52875, refers to a carriage return line feed (CRLF) injection attack, paving the way for HTTP response splitting, which could then lead to a cross-site scripting (XSS) flaw. Successful exploitation of the 1-click RCE flaw permits an attacker to inject malicious inputs into HTTP response headers by introducing carriage return (\r) and line feed (\n) characters. The flaw impacts KerioControl versions 9.2.5 through 9.4.5, according to security researcher Egidio Romano, who discovered and reported the flaw in early November 2024. The HTTP response splitting flaws have been uncovered in the following URI paths - "User input passed to these pages via the 'dest' GET parameter is not properly sanitized before being used to generate a 'Location' HTTP header in a 302 HTTP response," Romano said. "Specifically, the application does not correctly filter/remove line feed (LF) characters. This can be exploited to perform HTTP Response Splitting attacks, which, in turn, might allow it to carry out reflected cross-site scripting (XSS) and possibly other attacks." A fix for the vulnerability was released by GFI on December 19, 2024, with version 9.4.5 Patch 1. A proof-of-concept (PoC) exploit has since been made available. Specifically, an adversary could craft a malicious URL such that an administrator user clicking on it triggers the execution of the PoC hosted on an attacker-controlled server, which then uploads a malicious .img file via the firmware upgrade functionality, granting root access to the firewall. Threat intelligence firm GreyNoise has reported that exploitation attempts targeting CVE-2024-52875 commenced back on December 28, 2024, with the attacks originating from seven unique IP addresses from Singapore and Hong Kong to date. According to Censys, there are more than 23,800 internet-exposed GFI KerioControl instances. A majority of these servers are located in Iran, Uzbekistan, Italy, Germany, the United States, Czechia, Belarus, Ukraine, Russia, and Brazil. The exact nature of the attacks exploiting the flaw is presently not known. Users of KerioControl are advised to take steps to secure their instances as soon as possible to mitigate potential threats.