CVE-2026-22781 is an OS command injection vulnerability identified in the TinyWeb HTTP server, a lightweight web server written in Delphi for Win32 platforms. Versions of TinyWeb prior to 1.98 improperly handle CGI ISINDEX-style query parameters by passing them directly as command-line arguments to CGI executables using the Windows CreateProcess() API. This lack of input sanitization allows attackers to inject Windows shell metacharacters into HTTP requests, enabling execution of arbitrary OS commands on the server. The vulnerability requires no authentication or user interaction, making it remotely exploitable by any attacker with network access to the server. The impact is severe, as arbitrary code execution can lead to full system compromise, data theft, or service disruption. The vulnerability is classified under CWE-78 (Improper Neutralization of Special Elements used in an OS Command) and has a CVSS 4.0 base score of 10.0, reflecting its critical nature with high impact on confidentiality, integrity, and availability. Although no known exploits have been reported in the wild, the straightforward exploitation method and critical severity necessitate urgent remediation. The vendor has addressed the issue in TinyWeb version 1.98, which properly sanitizes input parameters to prevent command injection.

For European organizations, this vulnerability poses a significant risk, particularly for those using TinyWeb servers in production environments or exposing them to the internet. Successful exploitation can lead to complete compromise of affected servers, allowing attackers to execute arbitrary commands, potentially leading to data breaches, ransomware deployment, lateral movement within networks, or disruption of critical services. Given the unauthenticated and remote nature of the exploit, attackers can operate stealthily and at scale. Organizations in sectors such as finance, healthcare, government, and critical infrastructure, which often rely on Windows-based web services, are at heightened risk. The vulnerability could also be leveraged to establish persistent footholds or pivot to other internal systems, amplifying the impact. The absence of known exploits in the wild currently provides a window for proactive defense, but the critical severity demands immediate attention to avoid potential future attacks.

European organizations should immediately upgrade TinyWeb servers to version 1.98 or later, where the vulnerability is fixed. If upgrading is not immediately feasible, implement network-level controls such as firewall rules to restrict access to the TinyWeb server, limiting exposure to trusted IP addresses only. Disable or restrict CGI ISINDEX functionality if not required, as this is the attack vector. Employ web application firewalls (WAFs) with custom rules to detect and block suspicious query parameters containing shell metacharacters. Conduct thorough audits of all systems running TinyWeb to identify vulnerable instances. Monitor server logs for unusual command execution patterns or unexpected CGI requests. Implement strict input validation and sanitization on any custom CGI scripts or web applications interfacing with TinyWeb. Finally, ensure robust endpoint detection and response (EDR) solutions are in place to detect potential exploitation attempts and respond rapidly.