CVE-2025-43786 is a medium severity vulnerability classified under CWE-79, which pertains to improper neutralization of input during web page generation, commonly known as Cross-site Scripting (XSS). This vulnerability affects multiple versions of the Liferay Portal, specifically versions 7.4.0 through 7.4.3.128, and various releases of Liferay DXP from 2023.Q4.0 up to 2024.Q3.1. The core issue involves the enumeration of ERC (Entity Resource Codes) from object entries within the portal. Attackers can exploit this vulnerability by leveraging differences in response times to determine the existence of specific ERCs in the application. This timing side-channel allows an attacker to infer sensitive information about the application's internal state without requiring authentication or user interaction. The CVSS 4.0 base score is 6.9, indicating a medium severity level. The vector string (AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N) shows that the attack can be performed remotely over the network with low attack complexity, no privileges or user interaction required, and impacts confidentiality to a limited extent. The vulnerability does not affect integrity or availability directly. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability arises from improper input validation and output encoding in the web page generation process, allowing attackers to perform timing attacks to enumerate valid ERCs, which could be leveraged as a reconnaissance step for further attacks or information gathering within the Liferay Portal environment.

For European organizations using Liferay Portal or Liferay DXP, this vulnerability poses a risk primarily in terms of information disclosure. Attackers can remotely enumerate valid ERCs, which may reveal sensitive internal identifiers or resource mappings. While this does not directly lead to code execution or data modification, it can facilitate targeted attacks such as more precise phishing, privilege escalation attempts, or further exploitation of other vulnerabilities by providing attackers with detailed knowledge of the system's structure. Given that Liferay Portal is widely used by enterprises, government agencies, and public sector organizations across Europe for content management and collaboration, the exposure of such internal information could undermine confidentiality and trust. The lack of required authentication or user interaction increases the risk profile, as attackers can scan and enumerate ERCs without needing credentials or user involvement. However, the limited impact on integrity and availability and the absence of known active exploits reduce the immediate criticality. Still, the vulnerability should be addressed promptly to prevent attackers from leveraging this reconnaissance capability in multi-stage attacks.

European organizations should implement the following specific mitigation measures: 1) Monitor Liferay's official security advisories closely and apply patches or updates as soon as they become available to address CVE-2025-43786. 2) In the interim, restrict access to Liferay Portal management interfaces and APIs to trusted IP ranges using network-level controls such as firewalls or VPNs to limit exposure to potential attackers. 3) Employ Web Application Firewalls (WAFs) with custom rules to detect and block anomalous request patterns indicative of timing enumeration attacks targeting ERCs. 4) Conduct thorough input validation and output encoding reviews in custom Liferay modules or extensions to ensure no additional XSS or timing side channels exist. 5) Implement logging and alerting on unusual access patterns or repeated requests that may indicate enumeration attempts. 6) Educate security teams and developers on the risks of timing attacks and the importance of secure coding practices in web page generation. 7) Consider deploying runtime application self-protection (RASP) solutions that can detect and block exploitation attempts in real time. These measures, combined with timely patching, will reduce the risk of exploitation and limit the attack surface.