CVE-2024-39888 is a high-severity vulnerability affecting Siemens Mendix Encryption versions 10.0.0 up to but not including 10.0.2. The core issue stems from the use of a hard-coded, security-relevant constant — specifically, a default EncryptionKey value embedded within the Mendix Encryption module. This default key is utilized in projects where no custom EncryptionKey has been explicitly set by the user or developer. Because this key is hard-coded and publicly known or easily discoverable, an attacker can leverage it to decrypt any encrypted project data that relies on this default key. The vulnerability falls under CWE-547, which concerns the use of hard-coded security constants, a recognized poor security practice that can lead to compromise of confidentiality. The CVSS 3.1 base score is 7.5, indicating a high severity, with the vector AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. This means the vulnerability is remotely exploitable over the network without any privileges or user interaction, and it results in a complete loss of confidentiality (C:H) but does not affect integrity or availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability impacts the confidentiality of encrypted data within Mendix applications that rely on the default key, potentially exposing sensitive business or operational data to unauthorized parties. Since Mendix is a low-code application development platform widely used for enterprise applications, this vulnerability could affect a broad range of business-critical applications that use Mendix Encryption without custom keys, especially in environments where encryption is relied upon to protect sensitive data at rest or in transit within the application context.

For European organizations, the impact of this vulnerability can be significant, particularly for those using Mendix platform applications that employ the affected encryption module without specifying a unique encryption key. Confidential data such as personal information, intellectual property, financial records, or operational data could be decrypted by attackers, leading to data breaches and compliance violations under regulations like GDPR. The ease of exploitation (no authentication or user interaction required) increases the risk of automated or opportunistic attacks, potentially affecting cloud-hosted Mendix applications or on-premises deployments accessible over the network. The loss of confidentiality could damage organizational reputation, result in financial penalties, and disrupt trust with customers and partners. Given that Mendix is used across various sectors including manufacturing, finance, healthcare, and public services in Europe, the vulnerability could have cross-sectoral impacts. However, since integrity and availability are not impacted, the threat is primarily data exposure rather than system disruption or data manipulation.

To mitigate this vulnerability, European organizations should immediately audit their Mendix applications to identify any projects using Mendix Encryption version 10.0.0 without a custom EncryptionKey configured. They should enforce the use of unique, strong encryption keys per project to eliminate reliance on the default hard-coded key. Until Siemens releases an official patch or update, organizations can implement compensating controls such as encrypting sensitive data at a higher application layer with custom keys or using external encryption services. Network-level protections like restricting access to Mendix application endpoints and monitoring for unusual decryption attempts can reduce exposure. Additionally, organizations should plan to upgrade to Mendix Encryption version 10.0.2 or later once available, as these versions presumably address the vulnerability. Regular security reviews and penetration testing focused on encryption key management practices within Mendix projects are recommended to prevent similar issues. Finally, educating developers and administrators about the risks of hard-coded keys and enforcing secure key management policies will help mitigate future risks.