CVE-2025-34309 is a stored cross-site scripting (XSS) vulnerability identified in IPFire, an open-source firewall distribution widely used for network security. The flaw exists in versions prior to 2.29 (Core Update 198) and affects the Dynamic DNS host management functionality. Specifically, when an authenticated user creates or edits a Dynamic DNS host, the SERVICE, LOGIN, and PASSWORD parameters are submitted via an HTTP POST request to /cgi-bin/ddns.cgi. These parameters are stored and later rendered in the web interface without proper input sanitization or output encoding. Consequently, an attacker with valid credentials can inject malicious JavaScript code into these fields. When other users view or edit the affected Dynamic DNS entries, the injected scripts execute in their browsers within the context of the IPFire web interface. This can lead to session hijacking, unauthorized actions, or information disclosure. The vulnerability requires authentication but no additional user interaction beyond accessing the affected pages. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N) reflects network attack vector, low attack complexity, no privileges required beyond authenticated access, and partial scope impact. While no known exploits are currently reported in the wild, the vulnerability poses a tangible risk to IPFire deployments, especially those with multiple administrators or users accessing the web interface.

For European organizations, the impact of this vulnerability can be significant, particularly for those relying on IPFire as a perimeter or internal firewall solution. Successful exploitation could allow attackers to execute arbitrary JavaScript in the context of the IPFire web interface, potentially leading to session hijacking of administrative accounts, unauthorized configuration changes, or leakage of sensitive network information. This could compromise the integrity and availability of network security controls. Given that IPFire is often deployed in small to medium enterprises and critical infrastructure environments, exploitation could disrupt network operations or facilitate further lateral movement by attackers. The requirement for authenticated access limits the attack surface to insiders or compromised accounts, but phishing or credential theft could enable such access. The medium CVSS score reflects moderate risk, but the potential for privilege escalation and persistent access makes it a concern for organizations with sensitive network environments.

European organizations should immediately upgrade IPFire installations to version 2.29 (Core Update 198) or later, where this vulnerability is addressed. If upgrading is not immediately feasible, administrators should restrict access to the IPFire web interface to trusted networks and enforce strong authentication mechanisms, including multi-factor authentication, to reduce the risk of credential compromise. Regularly audit Dynamic DNS host entries for suspicious or unexpected content in SERVICE, LOGIN, and PASSWORD fields. Implement web application firewall (WAF) rules to detect and block common XSS payloads targeting the /cgi-bin/ddns.cgi endpoint. Additionally, educate administrators about the risks of stored XSS and encourage cautious handling of Dynamic DNS configurations. Monitoring logs for unusual POST requests to the ddns.cgi endpoint can help detect exploitation attempts. Finally, isolate IPFire management interfaces from general user networks to limit exposure.