CVE-2025-34303 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) within the web management interface. Specifically, the vulnerability arises from improper neutralization of input in the IGNORE_ENTRY_REMARK parameter when an authenticated user adds a whitelisted host. The parameter value is submitted via an HTTP POST request to /cgi-bin/ids.cgi and stored without proper sanitization or encoding. Consequently, malicious JavaScript code injected into this parameter is executed in the browsers of other users who view the affected whitelist entry. This stored XSS can be leveraged by attackers to perform actions such as session hijacking, credential theft, or executing unauthorized commands within the IPFire interface. Exploitation requires the attacker to have authenticated access to the system, but no further user interaction is necessary once the malicious remark is stored. The vulnerability is rated medium severity with a CVSS 4.0 score of 5.1, reflecting its network attack vector, low attack complexity, and lack of required privileges beyond authentication. No public exploits have been reported yet, but the risk remains significant for environments relying on IPFire for perimeter security. The vulnerability highlights the importance of proper input validation and output encoding in web applications, especially those managing critical network infrastructure.

For European organizations, the impact of CVE-2025-34303 can be substantial, particularly for those deploying IPFire as a firewall or security gateway. Successful exploitation could allow an authenticated attacker to execute arbitrary JavaScript in the context of other administrative users, potentially leading to session hijacking, unauthorized configuration changes, or disclosure of sensitive management information. This undermines the confidentiality and integrity of the firewall management interface and could facilitate further network compromise. Given IPFire’s role in protecting internal networks, exploitation could cascade into broader security incidents, affecting availability indirectly through misconfiguration or disruption. Organizations in sectors with stringent regulatory requirements, such as finance, healthcare, and critical infrastructure, may face compliance risks if such vulnerabilities are exploited. The medium severity rating suggests that while the vulnerability is not trivially exploitable by unauthenticated attackers, the requirement for authentication does not eliminate the risk, especially in environments with multiple administrators or weak credential management. The lack of known exploits in the wild provides a window for proactive mitigation before active attacks emerge.

To mitigate CVE-2025-34303, European organizations should prioritize upgrading IPFire installations to version 2.29 (Core Update 198) or later, where the vulnerability is addressed. If immediate patching is not 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 unauthorized access. Regularly audit whitelist entries and other user-generated content for suspicious or unexpected remarks that could indicate attempted exploitation. Implement web application firewall (WAF) rules to detect and block suspicious input patterns targeting the IGNORE_ENTRY_REMARK parameter. Additionally, organizations should educate administrators about the risks of stored XSS and encourage cautious handling of input fields in management interfaces. Monitoring logs for unusual POST requests to /cgi-bin/ids.cgi can help detect exploitation attempts. Finally, consider isolating management interfaces from general user networks and employing network segmentation to limit the impact of any compromise.