CVE-2025-21066 is a medium-severity vulnerability classified as CWE-125 (Out-of-bounds Read) found in the SPI decoder component of Samsung Notes, a note-taking application on Samsung mobile devices. The flaw exists in versions prior to 4.4.30.63 and allows a local attacker to read memory outside the intended buffer boundaries. This out-of-bounds read can lead to the disclosure of sensitive information stored in adjacent memory regions, potentially exposing confidential data or application internals. The vulnerability does not require any privileges or user interaction, but the attacker must have local access to the device, such as through physical access or via a compromised local user account. The CVSS v3.1 base score is 4.0, reflecting a low attack vector (local), low complexity, no privileges required, no user interaction, and an impact limited to integrity (memory disclosure) without affecting confidentiality or availability. No known exploits have been reported in the wild, and no official patches have been linked yet, although Samsung has reserved the CVE and published the advisory. The vulnerability arises from improper bounds checking in the SPI decoder, which processes specific data formats within Samsung Notes. Exploitation could allow attackers to read unintended memory areas, which might contain sensitive information or aid in further attacks. Given the local access requirement, the threat is mainly to environments where device access is not tightly controlled or where malicious insiders or malware have local footholds.

For European organizations, the primary impact of CVE-2025-21066 is the potential leakage of sensitive information through out-of-bounds memory reads on Samsung mobile devices running vulnerable versions of Samsung Notes. This could lead to exposure of confidential notes, credentials, or other sensitive data stored or processed by the app. Although the vulnerability does not directly compromise confidentiality or availability, the integrity impact could facilitate further attacks or data manipulation. Organizations with bring-your-own-device (BYOD) policies or mobile workforce using Samsung devices are at higher risk, especially if local device access controls are weak. The lack of known exploits reduces immediate risk, but the vulnerability could be leveraged in targeted attacks or combined with other local exploits. The medium severity suggests moderate urgency in patching, but organizations handling sensitive or regulated data should prioritize mitigation to prevent potential data leakage and comply with data protection regulations such as GDPR.

1. Update Samsung Notes to version 4.4.30.63 or later as soon as the patch is released by Samsung to address the out-of-bounds read vulnerability. 2. Restrict local access to Samsung mobile devices by enforcing strong device authentication methods such as biometrics or PINs and limiting physical access to trusted personnel only. 3. Implement mobile device management (MDM) solutions to enforce application updates and restrict installation of unauthorized apps that could exploit local vulnerabilities. 4. Monitor devices for unusual local activity or signs of compromise that could indicate attempts to exploit local vulnerabilities. 5. Educate users on the risks of local device access and encourage secure handling of devices, especially in shared or public environments. 6. For highly sensitive environments, consider disabling or limiting the use of Samsung Notes until the vulnerability is patched. 7. Regularly audit and review device security policies to ensure compliance with best practices for local access control and application security.