CVE-2026-26279 in Froxlor
Summary
by MITRE • 03/04/2026
Froxlor is open source server administration software. Prior to 2.3.4, a typo in Froxlor's input validation code (== instead of =) completely disables email format checking for all settings fields declared as email type. This allows an authenticated admin to store arbitrary strings in the panel.adminmail setting. This value is later concatenated into a shell command executed as root by a cron job, where the pipe character | is explicitly whitelisted. The result is full root-level Remote Code Execution. This vulnerability is fixed in 2.3.4.
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Analysis
by VulDB Data Team • 03/04/2026
The vulnerability identified as CVE-2026-26279 represents a critical security flaw in Froxlor, an open-source server administration software platform. This issue stems from a fundamental coding error in the input validation mechanism that affects how email address formats are verified within the application's configuration settings. The flaw manifests as a simple but devastating typo in the comparison operator used for validating email inputs, where double equals (==) is incorrectly implemented instead of single equals (=) for proper string comparison operations. This seemingly minor coding mistake has profound implications for the software's security posture and ultimately leads to complete system compromise.
The technical execution of this vulnerability begins with the misconfigured input validation that allows arbitrary strings to be stored in the panel.adminmail configuration setting, which should normally be restricted to valid email address formats. This misconfiguration occurs because the email type validation logic fails to properly verify the format of input strings, essentially disabling all email format checking for fields declared as email type. When an authenticated administrator modifies this setting with malicious input, the system accepts any string value without proper validation. The vulnerability becomes exploitable when the Froxlor application subsequently uses this stored value in a shell command execution context, where the value is concatenated into a system command that runs with root privileges. The cron job responsible for executing this command operates with elevated permissions, creating a direct path for privilege escalation.
The operational impact of this vulnerability extends far beyond simple data corruption or unauthorized access. The combination of the input validation bypass and the root-level command execution creates a full remote code execution scenario that allows attackers to gain complete system control. The vulnerability specifically exploits the concatenation of the malicious adminmail value into a shell command that executes with root privileges, where the pipe character | is explicitly whitelisted in the command execution environment. This whitelisting of the pipe character provides attackers with additional flexibility in crafting malicious payloads that can be executed through the vulnerable command chain. The attack vector requires only authentication to the Froxlor administration panel, making it particularly dangerous as it can be exploited by anyone with administrative access credentials.
Security practitioners should note that this vulnerability aligns with CWE-20, which describes improper input validation as a fundamental weakness in software applications. The flaw demonstrates how a simple programming error can create a severe security vulnerability, particularly when combined with command injection opportunities in privileged execution contexts. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and command execution capabilities, where the initial access through authentication leads to full system compromise. The vulnerability also reflects poor secure coding practices related to input validation and privilege separation, as the system fails to properly validate user inputs before using them in security-critical operations. Organizations using Froxlor should immediately upgrade to version 2.3.4 or later, which contains the necessary fixes to correct the input validation logic and prevent this class of vulnerability from being exploited.