CVE-2026-40187 in egroupware
Summary
by MITRE • 07/20/2026
In egroupware version 26.0 and earlier, an authenticated administrator can achieve OS-level Remote Code Execution (RCE) by uploading a malicious eTemplate XML file (`.xet`) to the VFS `/etemplates` mount. The `Widget::expand_name()` method passes template widget attribute values directly into a PHP `eval()` call with only double-quote escaping applied - **backtick characters are not escaped**. In PHP, backticks inside a double-quoted `eval()` string execute shell commands. This allows an admin-level user to escalate from web application access to arbitrary OS command execution on the server.
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Analysis
by VulDB Data Team • 07/20/2026
The vulnerability in egroupware version 26.0 and earlier represents a critical security flaw that enables authenticated administrators to achieve full operating system compromise through a carefully crafted file upload attack. This vulnerability stems from improper input validation and sanitization within the application's template processing mechanism, specifically affecting the VFS `/etemplates` mount point where malicious files can be uploaded by authenticated users with administrative privileges.
The technical exploitation occurs through the Widget::expand_name() method which processes template widget attribute values without adequate sanitization before passing them to a PHP eval() function. While the implementation does apply double-quote escaping to prevent typical injection scenarios, it fails to escape backtick characters that hold special meaning in PHP's double-quoted string context. This omission creates a critical pathway for command execution since PHP interprets backticks as shell command delimiters within double-quoted strings, effectively allowing attackers to execute arbitrary operating system commands through the web application interface.
This vulnerability directly maps to CWE-94 (Improper Control of Generation of Code) and CWE-78 (Improper Neutralization of Special Elements used in OS Command) within the Common Weakness Enumeration framework, demonstrating how insufficient input sanitization can lead to remote code execution. The attack vector leverages the principle of least privilege by exploiting an authenticated administrative account to escalate from web application access to full system compromise, aligning with ATT&CK technique T1059.001 (Command and Scripting Interpreter: PowerShell) and T1078 (Valid Accounts) where attackers use legitimate administrative credentials to gain elevated privileges.
The operational impact of this vulnerability is severe as it allows attackers to execute arbitrary commands with the privileges of the web server process, potentially leading to complete system compromise, data exfiltration, or further lateral movement within the network. The vulnerability affects organizations using egroupware versions up to and including 26.0 where administrative users can upload files to the VFS mount point, making it particularly dangerous in environments where administrative accounts are compromised or when attackers gain access through other means.
Organizations should immediately apply patches or updates from egroupware vendors to address this vulnerability, ensuring that all administrative users have proper credential management and multi-factor authentication enabled. Network segmentation and monitoring should be implemented to detect unusual file upload activities, particularly targeting VFS mount points. Additionally, implementing web application firewalls with rule sets that can detect and block suspicious eval() usage patterns will provide additional defense-in-depth protection against similar vulnerabilities in the future.
The root cause of this vulnerability highlights the importance of proper input validation and sanitization practices, particularly when dealing with dynamic code execution contexts. Security practitioners should emphasize that all user-supplied data passed to eval() functions must undergo comprehensive sanitization, including escaping of all shell metacharacters beyond the basic double-quote escape. This vulnerability demonstrates why automated security tools and static analysis should flag any usage of eval() with unsanitized input as a high-risk pattern requiring immediate remediation.
This particular flaw represents a dangerous combination of authentication bypass requirements with privileged code execution capabilities, making it particularly attractive to attackers who can leverage administrative access for maximum impact. The vulnerability serves as a reminder that even authenticated access does not guarantee system security, as proper privilege separation and input validation remain critical defenses against command injection attacks. Organizations should conduct thorough security assessments of their web applications to identify similar patterns where dynamic code execution might occur without adequate sanitization controls.