CVE-2025-21020 is a vulnerability classified as CWE-787, an out-of-bounds write, found in the Samsung Mobile Blockchain Keystore component prior to version 1.3.17.2. The flaw occurs during the creation of bitmap images within the Blockchain Keystore, allowing a local attacker with privileged access to write data outside the bounds of allocated memory. This type of memory corruption can lead to overwriting critical data structures, potentially enabling privilege escalation or arbitrary code execution. The vulnerability requires local access with high privileges and does not require user interaction. The CVSS v3.1 score is 5.7 (medium severity), reflecting the complexity of exploitation (high attack complexity) and the need for privileged access, but with high impact on confidentiality and integrity. No known exploits are currently reported in the wild, and no patches or mitigation links are provided yet. The vulnerability affects Samsung Mobile devices running the Blockchain Keystore component, which is used to securely manage blockchain-related cryptographic keys and operations on Samsung smartphones. Given the nature of the vulnerability, exploitation could compromise the confidentiality and integrity of sensitive cryptographic keys stored in the keystore, undermining the security of blockchain transactions and related applications on affected devices.

For European organizations, especially those utilizing Samsung mobile devices for blockchain applications, this vulnerability poses a significant risk. Compromise of the Blockchain Keystore could lead to unauthorized access to cryptographic keys, enabling fraudulent blockchain transactions, identity theft, or unauthorized access to blockchain-based services. Organizations in finance, supply chain, and digital identity sectors that rely on blockchain technology could face data breaches, financial losses, and reputational damage. Since the vulnerability requires local privileged access, the risk is higher in environments where devices are shared, or where attackers can gain physical or administrative access to devices. The confidentiality and integrity of blockchain operations could be severely impacted, potentially disrupting business processes that depend on secure blockchain interactions.

To mitigate this vulnerability, European organizations should prioritize updating Samsung Mobile devices to Blockchain Keystore version 1.3.17.2 or later once patches are released. Until patches are available, organizations should enforce strict device access controls to prevent unauthorized local privileged access, including strong authentication, device encryption, and mobile device management (MDM) policies that limit administrative privileges. Monitoring for unusual local activity on devices and restricting the installation of untrusted applications can reduce the risk of exploitation. Additionally, organizations should conduct regular security audits of mobile devices used in blockchain operations and educate users on the risks of privilege escalation attacks. Implementing endpoint detection and response (EDR) solutions capable of detecting memory corruption attempts on mobile devices may also provide early warning of exploitation attempts.