CVE-2025-43770 is a reflected Cross-Site Scripting (XSS) vulnerability affecting multiple versions of the Liferay Portal and Liferay DXP products, specifically versions 7.4.0 through 7.4.3.131 and various 2024 quarterly releases up to Q4.3. This vulnerability arises due to improper neutralization of input during web page generation (CWE-79), where an attacker can inject malicious JavaScript code into the 'referer' or 'FORWARD_URL' parameters by exploiting the presence of null byte (%00) characters. The vulnerability is exploitable remotely without any authentication or user interaction, allowing an attacker to craft a specially crafted URL that, when visited by a victim, executes arbitrary JavaScript in the context of the vulnerable web application. This can lead to session hijacking, credential theft, or unauthorized actions performed on behalf of the user. The CVSS v4.0 base score is 6.9 (medium severity), reflecting the ease of exploitation (network vector, no privileges required, no user interaction) but limited impact on availability and integrity, with low to limited scope changes. No known exploits are reported in the wild yet, and no official patches or mitigations are linked in the provided data. The vulnerability affects widely used enterprise portal software that supports web content management, collaboration, and digital experience management, making it a significant concern for organizations relying on Liferay for their web infrastructure.

For European organizations, the impact of this vulnerability can be significant, especially for those using Liferay Portal or DXP as part of their digital infrastructure. Exploitation could lead to unauthorized access to sensitive information, session hijacking, and potential compromise of user accounts or administrative functions. This could result in data breaches, disruption of services, and reputational damage. Given the nature of XSS attacks, attackers could also use this vulnerability to deliver further malware or phishing attacks targeting employees or customers. Organizations in sectors such as government, finance, healthcare, and large enterprises that rely on Liferay for internal or external portals are particularly at risk. The vulnerability's ability to be exploited without authentication increases the attack surface, making it easier for remote attackers to target European entities. Additionally, compliance with GDPR and other data protection regulations means that exploitation leading to data exposure could result in regulatory penalties and legal consequences.

To mitigate this vulnerability, European organizations should prioritize the following actions: 1) Apply official patches or updates from Liferay as soon as they become available, ensuring all affected versions are upgraded to secure releases. 2) Implement Web Application Firewall (WAF) rules that detect and block suspicious input patterns, especially those containing null byte characters (%00) in URL parameters such as 'referer' and 'FORWARD_URL'. 3) Conduct thorough input validation and output encoding on all user-controllable parameters within the portal to prevent script injection. 4) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts within the portal environment. 5) Monitor web server and application logs for unusual request patterns indicative of attempted exploitation. 6) Educate users and administrators about the risks of clicking on untrusted links and encourage the use of secure browsing practices. 7) If immediate patching is not feasible, consider temporarily disabling or restricting access to vulnerable portal components or parameters to reduce exposure. These measures, combined with ongoing vulnerability management and security monitoring, will help reduce the risk posed by this XSS vulnerability.