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 of Liferay DXP. The vulnerability arises due to improper neutralization of input during web page generation, classified under CWE-79. An unauthenticated remote attacker can exploit this flaw by injecting malicious JavaScript code into the 'referer' or 'FORWARD_URL' parameters. The injection leverages the use of the null byte (%00) within these parameters to bypass input validation or filtering mechanisms. When a victim accesses a crafted URL or is redirected through the vulnerable portal, the injected script executes in the context of the victim's browser, potentially leading to session hijacking, credential theft, or other malicious actions. The vulnerability does not require any authentication or user interaction, increasing its risk profile. The CVSS v4.0 score is 6.9 (medium severity), reflecting network attack vector, low attack complexity, no privileges or user interaction required, and limited impact on confidentiality and integrity. No known exploits are currently reported in the wild, and no official patches have been linked yet. However, given the widespread use of Liferay Portal in enterprise environments, this vulnerability poses a tangible risk if left unmitigated.

For European organizations, the impact of CVE-2025-43770 can be significant, especially for those relying on Liferay Portal or DXP for their intranet, customer portals, or public-facing websites. Successful exploitation can lead to unauthorized script execution in users' browsers, enabling attackers to steal session cookies, perform actions on behalf of users, or deliver further malware. This can result in data breaches, loss of user trust, and regulatory non-compliance under GDPR due to exposure of personal data. The vulnerability's ability to be exploited without authentication or user interaction increases the risk of automated attacks and widespread exploitation. Organizations in sectors such as finance, government, healthcare, and e-commerce, which often use Liferay for digital services, may face operational disruptions and reputational damage. Additionally, the cross-site scripting flaw could be leveraged as a stepping stone for more complex attacks targeting internal systems or privileged accounts.

To mitigate CVE-2025-43770, European organizations should: 1) Immediately identify all instances of Liferay Portal and DXP in their environment and verify the versions against the affected list. 2) Monitor official Liferay security advisories for patches or updates addressing this vulnerability and apply them promptly once available. 3) Implement web application firewall (WAF) rules to detect and block suspicious requests containing null byte (%00) injections in the 'referer' and 'FORWARD_URL' parameters. 4) Conduct thorough input validation and output encoding on all user-controllable parameters, especially those reflected in web pages, to prevent script injection. 5) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. 6) Educate users and administrators about the risks of XSS and encourage vigilance against suspicious links or redirects. 7) Regularly audit and test web applications for XSS vulnerabilities using automated scanners and manual penetration testing. These steps, combined, will reduce the attack surface and limit the potential impact of this vulnerability.