CVE-2023-6013: Stored XSS in H2O

The stored XSS vulnerability in H2O allows an attacker to inject malicious scripts into the application. When other users interact with the affected areas, these scripts execute in their browsers, potentially stealing session cookies, redirecting them to malicious websites, or defacing the application. The subsequent Local File Inclusion (LFI) attack amplifies the impact, enabling attackers to read sensitive files from the server's file system. This could expose configuration data, source code, or even system credentials, leading to complete system compromise. The combination of XSS and LFI creates a high-risk scenario with significant potential for data breaches and system takeover.

1. Reserved2023-11-08
2. Published2023-11-16
3. Modified2024-11-27
4. EPSS updated2026-04-02

The primary mitigation is to upgrade to a patched version of H2O as soon as it becomes available. Until then, implement strict input validation and output encoding to prevent the injection of malicious scripts. Specifically, sanitize all user-supplied data before storing it in the database or displaying it in the application. Employ context-aware output encoding to ensure that any potentially harmful characters are properly escaped. Consider implementing a Web Application Firewall (WAF) with rules to detect and block XSS attacks. Regularly review and update security policies and procedures to address emerging threats.