CVE-2025-36396 is a cross-site scripting (XSS) vulnerability classified under CWE-79 affecting IBM Application Gateway versions 23.10 through 25.09. This vulnerability arises from improper neutralization of input during web page generation, allowing an authenticated user to inject arbitrary JavaScript code into the web UI. The injected script can manipulate the interface's intended behavior, potentially leading to the disclosure of sensitive information such as user credentials within an active trusted session. The vulnerability requires the attacker to have legitimate access credentials and to interact with the system to execute the attack, which limits the attack surface but does not eliminate risk. The vulnerability impacts confidentiality and integrity but does not affect availability. The CVSS 3.1 score of 5.4 reflects a medium severity, with network attack vector, low attack complexity, and privileges required. No patches or exploits are currently publicly available, but the vulnerability is officially published and should be addressed promptly. The issue highlights the importance of proper input validation and output encoding in web applications, especially in administrative interfaces that manage critical network functions.

For European organizations, this vulnerability poses a risk primarily to confidentiality and integrity of user sessions within IBM Application Gateway environments. If exploited, attackers could execute malicious scripts that steal session tokens or credentials, potentially leading to unauthorized access or lateral movement within corporate networks. This is particularly concerning for organizations relying on IBM Application Gateway for secure application access or as part of their network security infrastructure. The requirement for authentication and user interaction reduces the likelihood of widespread automated exploitation but does not eliminate targeted attacks, especially insider threats or compromised accounts. The impact is heightened in sectors with sensitive data such as finance, healthcare, and government, where credential compromise can lead to significant data breaches or operational disruptions. Additionally, the vulnerability could undermine trust in the security of the gateway, affecting compliance with European data protection regulations like GDPR if personal data is exposed.

Organizations should prioritize upgrading IBM Application Gateway to versions beyond 25.09 once patches are released by IBM. In the interim, implement strict input validation and output encoding on all user-supplied data within the web UI to prevent script injection. Enforce the principle of least privilege to limit the number of users with access to the vulnerable interface. Employ multi-factor authentication (MFA) to reduce the risk of credential compromise. Monitor logs for unusual activity indicative of XSS exploitation attempts, such as unexpected script execution or anomalous session behavior. Consider deploying web application firewalls (WAFs) with custom rules to detect and block XSS payloads targeting the gateway. Educate users about the risks of executing unknown scripts and the importance of session security. Finally, maintain an incident response plan tailored to web interface compromises to quickly contain and remediate any exploitation.