CVE-2025-52497 is a medium-severity vulnerability identified in Mbed TLS, a widely used open-source cryptographic library designed for embedded systems and IoT devices. The vulnerability is classified as a CWE-193 Off-by-one Error, specifically a one-byte heap-based buffer underflow occurring in the PEM parsing functionality. The affected functions are mbedtls_pem_read_buffer and two mbedtls_pk_parse functions, which process PEM-encoded cryptographic keys and certificates. This flaw arises when untrusted PEM input is parsed, causing the library to underflow the heap buffer by one byte. Such a memory corruption issue can lead to undefined behavior, including potential application crashes or memory corruption, which might be leveraged by attackers to cause denial of service or potentially execute arbitrary code under certain conditions. The vulnerability affects all versions of Mbed TLS prior to 3.6.4, and no known exploits are currently reported in the wild. The CVSS v3.1 base score is 4.8, reflecting a network attack vector with high attack complexity, no privileges required, no user interaction, and limited impact on confidentiality and availability, with no integrity impact. This indicates the vulnerability can be exploited remotely but requires specific conditions and crafted input to trigger. The lack of authentication and user interaction requirements increases the attack surface, but the high complexity and limited impact reduce the overall risk. The absence of an official patch link suggests that remediation involves upgrading to Mbed TLS version 3.6.4 or later, where the issue is fixed.

For European organizations, the impact of CVE-2025-52497 depends largely on the extent to which Mbed TLS is embedded within their infrastructure, particularly in IoT devices, embedded systems, and network appliances that rely on secure communications. Given Mbed TLS's popularity in resource-constrained environments, sectors such as manufacturing, automotive, healthcare, and critical infrastructure may be affected if devices use vulnerable versions. Exploitation could lead to denial of service conditions, disrupting operations or causing device malfunctions. Although the vulnerability's impact on confidentiality and integrity is limited, availability impacts could affect service continuity, especially in industrial control systems or medical devices. The medium severity and lack of known exploits reduce immediate risk, but the potential for future exploitation necessitates proactive mitigation. Organizations handling sensitive data or critical operations should prioritize assessment and remediation to prevent exploitation that could cascade into broader operational disruptions or facilitate further attacks.

European organizations should take the following specific steps beyond generic advice: 1) Conduct an inventory of all devices and applications using Mbed TLS, focusing on embedded and IoT devices where updates may be less frequent. 2) Verify the Mbed TLS version in use and prioritize upgrading to version 3.6.4 or later, which contains the fix for this vulnerability. 3) For devices where direct updates are not feasible, consider network-level protections such as filtering or monitoring for anomalous PEM input patterns that could trigger the vulnerability. 4) Implement strict input validation and sanitization on any interfaces that accept PEM-encoded data to reduce the risk of malicious input exploitation. 5) Engage with device vendors and suppliers to confirm patch availability and deployment plans. 6) Monitor security advisories for any emerging exploit reports or additional patches. 7) Incorporate this vulnerability into incident response and vulnerability management workflows to ensure timely detection and remediation.