CVE-2025-40632 is a cross-site scripting (XSS) vulnerability identified in Icewarp Mail Server version 11.4.0. This vulnerability arises from improper neutralization of input during web page generation, specifically related to the handling of the “lastLogin” cookie. An attacker can manipulate this cookie to inject malicious JavaScript code, which will then be executed when the affected page is rendered by the user’s browser. The vulnerability is classified under CWE-79, which covers improper neutralization of input leading to XSS attacks. The CVSS 4.0 base score is 2, indicating a low severity level. The vector details show that the attack requires an adjacent network attacker (AV:A), with high attack complexity (AC:H), no privileges required (PR:N), but user interaction is necessary (UI:A). The vulnerability does not impact confidentiality, integrity, or availability directly (VC:N, VI:N, VA:N), and the scope is limited (S:L). No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability was reserved in April 2025 and published in May 2025. Given the nature of XSS, the primary risk is the execution of arbitrary scripts in the context of the user’s session, potentially leading to session hijacking, phishing, or other client-side attacks if exploited successfully.

For European organizations using Icewarp Mail Server 11.4.0, this vulnerability poses a risk primarily to end users accessing the mail server’s web interface. Successful exploitation could allow attackers to execute malicious scripts in users’ browsers, potentially leading to theft of session cookies, unauthorized actions on behalf of the user, or delivery of phishing payloads. Although the CVSS score is low due to the requirement of user interaction and high attack complexity, the impact on confidentiality and user trust can be significant, especially in sectors handling sensitive communications such as finance, healthcare, or government. The vulnerability does not directly compromise server integrity or availability, but client-side exploitation can lead to indirect impacts such as credential theft or lateral movement if combined with other vulnerabilities. European organizations with remote or hybrid workforces relying on webmail access are particularly exposed. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time.

Given the lack of an official patch at the time of this report, organizations should implement several specific mitigations: 1) Restrict access to the Icewarp Mail Server web interface to trusted networks or VPNs to reduce exposure to adjacent network attackers. 2) Employ Content Security Policy (CSP) headers to limit the execution of unauthorized scripts in browsers accessing the mail server. 3) Educate users about the risks of interacting with suspicious links or emails that could trigger the XSS payload. 4) Monitor web server logs for unusual cookie modifications or suspicious requests targeting the lastLogin cookie. 5) Consider deploying web application firewalls (WAFs) with custom rules to detect and block attempts to inject malicious scripts via cookies. 6) Plan for prompt upgrade or patch deployment once Icewarp releases a fix. 7) Implement multi-factor authentication (MFA) to reduce the impact of potential session hijacking. These measures go beyond generic advice by focusing on network access controls, user awareness, and proactive detection tailored to the specific vulnerability vector.