CVE-2025-21029 is a vulnerability identified in Samsung Mobile Devices, specifically related to the System UI component prior to the SMR (Security Maintenance Release) September 2025 Release 1. The vulnerability is classified under CWE-280, which pertains to improper handling of insufficient permissions. In this case, the flaw allows local attackers—meaning an attacker with physical or logical local access to the device—to send arbitrary replies to messages directly from the cover display interface. The cover display is a secondary screen on some Samsung devices that allows limited interaction without unlocking the main device. Due to improper permission checks, the System UI does not adequately verify whether the user or process has the necessary permissions to send message replies via this interface. This can lead to unauthorized message responses being sent without the device owner's consent or knowledge. The CVSS v3.1 base score is 4.0, indicating a medium severity level. The vector string (AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N) shows that the attack requires local access (AV:L), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no confidentiality impact (C:N), low integrity impact (I:L), and no availability impact (A:N). There are no known exploits in the wild at this time, and no patches or mitigations have been explicitly linked in the provided data. This vulnerability could be leveraged by malicious local actors to manipulate messaging functions stealthily, potentially facilitating social engineering, misinformation, or unauthorized communication on the device without escalating privileges or requiring user interaction.

For European organizations, this vulnerability poses a moderate risk primarily in scenarios where Samsung Mobile Devices are used as part of corporate communications or BYOD (Bring Your Own Device) policies. The ability for a local attacker to send arbitrary message replies without proper permissions could lead to unauthorized information disclosure or manipulation of communication channels. Although the confidentiality impact is rated as none, the integrity of message content can be compromised, which may result in misinformation or unauthorized instructions being sent from a legitimate device. This could affect internal communications, customer interactions, or operational workflows relying on mobile messaging. The threat is more pronounced in environments where devices are shared, left unattended, or accessible to untrusted individuals. However, since exploitation requires local access and no user interaction, remote attackers or phishing campaigns are unlikely vectors. The lack of availability impact means device functionality remains intact, but trust in message authenticity could be undermined. Organizations handling sensitive communications or operating in regulated sectors such as finance, healthcare, or government should be particularly cautious, as message integrity is critical. Additionally, the vulnerability could be exploited in targeted attacks against executives or personnel with access to sensitive information via mobile messaging.

To mitigate CVE-2025-21029 effectively, European organizations should: 1) Ensure all Samsung Mobile Devices are updated promptly with the SMR September 2025 Release 1 or later, as this release addresses the vulnerability. 2) Implement strict physical security controls to prevent unauthorized local access to devices, including screen lock policies, biometric authentication, and timeout settings for the cover display. 3) Enforce mobile device management (MDM) policies that restrict or monitor the use of cover display features and messaging applications, potentially disabling cover display replies if feasible. 4) Educate users about the risks of leaving devices unattended and encourage reporting of suspicious device behavior. 5) Monitor messaging logs and alerts for anomalous outgoing messages that could indicate exploitation attempts. 6) Consider deploying endpoint detection and response (EDR) solutions capable of detecting unusual local activity on mobile devices. 7) For high-risk environments, restrict the use of Samsung devices with vulnerable System UI versions or isolate them from sensitive communication channels until patched. These steps go beyond generic advice by focusing on controlling local access, leveraging device management capabilities, and monitoring for exploitation indicators specific to this vulnerability.