CVE-2025-31029 is a stored Cross-site Scripting (XSS) vulnerability identified in the bingu replyMail product, affecting all versions up to and including 1.2.0. The vulnerability stems from improper neutralization of user-supplied input during the generation of web pages, which allows malicious scripts to be stored on the server and subsequently executed in the browsers of users who view the affected content. This type of vulnerability can enable attackers to perform actions such as stealing session cookies, defacing web content, or redirecting users to malicious sites. The CVSS 3.1 base score is 5.4, reflecting a medium severity level, with the vector indicating network attack vector (AV:N), low attack complexity (AC:L), requiring privileges (PR:L), requiring user interaction (UI:R), and a scope change (S:C) with low confidentiality and integrity impacts but no availability impact. Exploitation requires an attacker to have some level of authenticated access to submit malicious input, and victims must interact with the malicious content for the attack to succeed. No known exploits are currently reported in the wild. The vulnerability was reserved in March 2025 and published in November 2025, with no official patches yet linked. The risk lies primarily in the potential for attackers to leverage this vulnerability to compromise user sessions or exfiltrate sensitive information via client-side script execution.

For European organizations, the impact of CVE-2025-31029 can be significant in environments where bingu replyMail is used for internal or external email communication. Successful exploitation could lead to unauthorized disclosure of sensitive information, session hijacking, or manipulation of email content, undermining trust and confidentiality. Sectors such as finance, government, healthcare, and critical infrastructure that rely heavily on secure email communications are particularly at risk. The medium severity rating suggests that while the vulnerability is not trivially exploitable without some privileges and user interaction, the consequences can affect data integrity and confidentiality. Additionally, the scope change in the CVSS vector indicates that the vulnerability can affect resources beyond the initially vulnerable component, potentially impacting multiple users or systems. European organizations with less mature security controls or limited patch management processes may face increased risk. The absence of known exploits currently provides a window for proactive mitigation before widespread attacks occur.

To mitigate CVE-2025-31029, European organizations should implement the following specific measures: 1) Monitor for and apply official patches or updates from bingu promptly once available to address the vulnerability at the source. 2) Implement strict input validation and output encoding on all user-supplied data within replyMail to prevent malicious script injection. 3) Restrict user privileges to the minimum necessary, limiting the ability of attackers to submit malicious content. 4) Employ Content Security Policy (CSP) headers to reduce the impact of potential XSS by restricting the execution of unauthorized scripts. 5) Conduct regular security audits and penetration testing focused on web application vulnerabilities, including stored XSS. 6) Educate users about the risks of interacting with suspicious email content to reduce the likelihood of successful exploitation. 7) Utilize web application firewalls (WAFs) with rules designed to detect and block XSS payloads targeting replyMail. 8) Monitor logs for unusual input patterns or user behavior indicative of exploitation attempts. These targeted actions go beyond generic advice by focusing on the specific context and exploitation requirements of this vulnerability.