CVE-2025-14020 is a user interface spoofing vulnerability identified in the LINE client for Android, specifically affecting versions prior to 14.20. The vulnerability resides in the in-app browser component, where a full-screen security Toast notification—intended to alert users to the security context—is not properly re-displayed when users return to the app after switching to another application. This failure creates an opportunity for attackers to craft phishing attacks by mimicking legitimate UI elements, thereby deceiving users into divulging sensitive information or performing unintended actions. The vulnerability is classified under CWE-451 (User Interface Misrepresentation). The CVSS 3.1 base score is 5.4, indicating a medium severity level with network attack vector (AV:N), low attack complexity (AC:L), no privileges required (PR:N), but requiring user interaction (UI:R). The impact affects confidentiality and integrity to a limited extent, with no impact on availability. No patches or exploits are currently reported, but the vulnerability is publicly disclosed as of December 15, 2025. This issue primarily targets the Android platform and affects users who rely on LINE’s in-app browser for web content, particularly when multitasking between apps.

For European organizations, this vulnerability poses a moderate phishing risk, especially in sectors where LINE is widely used for communication, such as in multinational corporations with Asian-European ties or companies with employees who use LINE for business communications. Attackers could exploit this UI spoofing flaw to impersonate trusted interfaces, potentially leading to credential theft, unauthorized access, or data leakage. The impact on confidentiality and integrity is limited but non-negligible, as phishing attacks can facilitate further compromise. Since the vulnerability requires user interaction and targets the in-app browser, the scope is limited to users who browse web content within LINE and switch between apps frequently. The absence of known exploits reduces immediate risk, but the potential for social engineering attacks remains. Organizations with employees using Android devices and LINE should consider this vulnerability in their threat models, particularly in industries with high phishing exposure such as finance, healthcare, and government.

1. Update the LINE client for Android to version 14.20 or later as soon as the patch is released to ensure the UI spoofing vulnerability is resolved. 2. Educate users about the risks of phishing attacks within in-app browsers, emphasizing caution when switching between apps and interacting with unexpected UI elements. 3. Implement mobile device management (MDM) policies that enforce app updates and restrict installation of outdated or untrusted applications. 4. Encourage users to verify URLs and security indicators manually when using in-app browsers, and to avoid entering sensitive information unless certain of the legitimacy. 5. Monitor for suspicious activity related to phishing attempts targeting LINE users, including unusual login patterns or reports of credential compromise. 6. Consider deploying endpoint protection solutions that can detect and block phishing attempts or malicious web content within mobile environments. 7. Collaborate with LINE Corporation for timely vulnerability disclosures and patch availability notifications.