CVE-2026-22903 is a stack-based buffer overflow vulnerability identified in the WAGO 0852-1322 device, which uses a modified version of the lighttpd web server. The vulnerability stems from improper handling of the SESSIONID cookie in HTTP requests. Specifically, when an attacker sends a crafted HTTP request containing an overly long SESSIONID cookie, the server's buffer allocated on the stack is overflowed. This overflow can cause the server process to crash (denial of service) or, more critically, enable remote code execution due to the absence of stack protection mechanisms such as stack canaries or address space layout randomization (ASLR). The vulnerability is exploitable remotely without requiring any authentication or user interaction, increasing its risk profile. The CVSS v3.1 score of 9.8 reflects the high impact on confidentiality, integrity, and availability, combined with the ease of exploitation. The affected product, WAGO 0852-1322, is typically used in industrial automation and control systems, where availability and integrity are paramount. Although no public exploits have been reported yet, the vulnerability's characteristics make it a prime candidate for future exploitation. The lack of available patches at the time of publication necessitates immediate defensive measures to mitigate potential attacks.

For European organizations, the impact of this vulnerability is significant, especially those operating in industrial automation, manufacturing, and critical infrastructure sectors where WAGO 0852-1322 devices are deployed. Exploitation can lead to complete system compromise, allowing attackers to disrupt operations by crashing devices or executing arbitrary code remotely. This could result in operational downtime, safety risks, data breaches, and potential sabotage of industrial processes. The loss of availability and integrity in control systems can have cascading effects on supply chains and public safety. Confidentiality may also be compromised if attackers gain control and extract sensitive operational data. Given the critical nature of these systems, the vulnerability poses a direct threat to business continuity and national infrastructure security within Europe.

1. Immediate network segmentation should be implemented to isolate WAGO 0852-1322 devices from general IT networks and the internet, limiting exposure to untrusted sources. 2. Deploy web application firewalls (WAFs) or intrusion prevention systems (IPS) configured to detect and block HTTP requests with abnormally long cookies or suspicious SESSIONID values. 3. Monitor network traffic for anomalous patterns indicative of exploitation attempts, such as repeated malformed HTTP requests targeting the SESSIONID cookie. 4. Engage with WAGO or authorized vendors to obtain patches or firmware updates as soon as they become available; prioritize patch management for affected devices. 5. Implement strict input validation and rate limiting on devices where possible to reduce the attack surface. 6. Conduct regular security audits and penetration testing focused on industrial control systems to identify and remediate similar vulnerabilities proactively. 7. Maintain up-to-date incident response plans tailored to industrial environments to quickly address potential exploitation events.