LISTSERV XSS (CVE-2022-39195)
Description
LISTSERV web interface contains a cross-site scripting (XSS) vulnerability in the 'c' parameter. This parameter accepts user input without proper sanitization or encoding, allowing attackers to inject malicious scripts that execute in the context of other users' browsers when they access specially crafted URLs.
Remediation
Apply the security patch by upgrading LISTSERV to version 17.0-2022a or later, which addresses CVE-2022-39195. If immediate patching is not possible, implement the following temporary mitigations:
1. Deploy a Web Application Firewall (WAF) with rules to detect and block XSS attempts in the 'c' parameter
2. Implement Content Security Policy (CSP) headers to restrict script execution:
Content-Security-Policy: default-src 'self'; script-src 'self'
3. Review web server logs for suspicious activity targeting the 'c' parameter
4. Educate users about the risks of clicking untrusted links to LISTSERV pages
After patching, verify the fix by testing that HTML/JavaScript in the 'c' parameter is properly encoded in the response.