CVE-2025-43739 is a medium-severity vulnerability affecting multiple versions of Liferay Portal and Liferay DXP, specifically versions 7.4.0 through 7.4.3.132 and various quarterly releases of Liferay DXP from 2024.Q1.1 through 2025.Q1.6. The vulnerability is categorized under CWE-203, which relates to Observable Discrepancies. In this case, any authenticated user within the affected Liferay Portal environment can modify the content of emails sent through the calendar portlet. This capability allows an attacker to craft and send phishing emails that appear to originate legitimately from the organization's calendar system to other users within the same organization. The vulnerability does not require elevated privileges beyond authentication, nor does it require user interaction beyond the attacker initiating the email modification. The CVSS 4.0 score is 5.3 (medium), indicating a moderate risk primarily due to the ability to conduct phishing attacks internally, potentially bypassing external email security controls. The attack vector is network-based with low attack complexity and no privileges required, but user interaction is needed to trigger the phishing email. The vulnerability impacts confidentiality by enabling phishing that could lead to credential theft or further compromise, but it does not directly affect system integrity or availability. No known exploits are currently reported in the wild, and no patches are linked yet, suggesting that mitigation may rely on configuration changes or monitoring until official fixes are released.

For European organizations using Liferay Portal or Liferay DXP, this vulnerability poses a significant risk of internal phishing attacks that can undermine trust in internal communications and lead to credential compromise or lateral movement within the network. Given that Liferay is widely used in enterprise intranet portals, customer portals, and collaboration platforms, the ability for any authenticated user to send manipulated calendar emails can facilitate targeted social engineering attacks. This is particularly concerning for sectors with sensitive data such as finance, healthcare, and government institutions prevalent in Europe. The internal nature of the phishing emails may bypass traditional email security gateways that focus on external threats, increasing the likelihood of successful attacks. Additionally, the vulnerability could be exploited to damage organizational reputation and disrupt business operations if phishing campaigns lead to data breaches or ransomware infections.

Until official patches are released, European organizations should implement the following specific mitigations: 1) Restrict calendar portlet access to only trusted users and minimize the number of users with email sending capabilities through this portlet. 2) Implement strict monitoring and alerting on calendar email content changes and unusual email sending patterns within the portal. 3) Educate users to verify unexpected calendar invitations or emails, especially those requesting sensitive information or containing links. 4) Employ internal email filtering solutions that inspect and flag suspicious internal emails, including those originating from the calendar system. 5) Review and tighten authentication and session management controls to prevent unauthorized access. 6) Coordinate with Liferay support for timely patch deployment once available and apply updates promptly. 7) Consider disabling the calendar portlet email functionality if not critical to operations until a fix is applied.