CVE-2025-48965 is a medium severity vulnerability identified in Mbed TLS, a widely used open-source cryptographic library designed for embedded systems and IoT devices. The flaw arises from an incorrect behavior order in the function mbedtls_asn1_store_named_data, which handles ASN.1 encoded data storage. Specifically, the vulnerability is a NULL pointer dereference triggered when the function processes conflicting data where the pointer val.p is NULL but the length val.len is greater than zero. This inconsistency can cause the software to dereference a NULL pointer, leading to a crash or denial of service (DoS). The vulnerability affects all versions of Mbed TLS prior to 3.6.4. The CVSS v3.1 base score is 4.0, indicating a medium severity level. The vector indicates that the attack vector is network-based (AV:N), requires high attack complexity (AC:H), no privileges (PR:N), no user interaction (UI:N), and the scope is changed (S:C). The impact is limited to availability (A:L), with no confidentiality or integrity impact. There are no known exploits in the wild as of the publication date, and no patches are linked yet. This vulnerability could be exploited remotely to cause a denial of service by crashing applications relying on Mbed TLS for cryptographic operations, potentially disrupting services or embedded devices that depend on secure communications. Given Mbed TLS's role in securing communications in embedded and IoT environments, this vulnerability could affect a broad range of devices and applications if exploited.

For European organizations, the impact of CVE-2025-48965 primarily involves potential denial of service conditions in systems using vulnerable versions of Mbed TLS. This could disrupt critical embedded systems, IoT devices, and network appliances that rely on Mbed TLS for secure communications. Sectors such as industrial control, telecommunications, healthcare devices, and smart infrastructure may be particularly vulnerable due to their reliance on embedded cryptographic libraries. While the vulnerability does not directly compromise confidentiality or integrity, service disruptions could lead to operational downtime, affecting business continuity and potentially causing cascading effects in critical infrastructure. Organizations with large deployments of embedded devices or IoT systems using Mbed TLS should be aware of the risk of remote crashes that could be triggered by attackers exploiting this flaw over the network. The medium severity rating suggests that while the impact is not catastrophic, the disruption could be significant in environments where availability is critical.

To mitigate CVE-2025-48965, European organizations should prioritize updating Mbed TLS to version 3.6.4 or later once patches become available. Until patches are released, organizations should conduct an inventory of all embedded systems, IoT devices, and network appliances using Mbed TLS and assess their exposure. Network-level mitigations include implementing strict ingress filtering and firewall rules to limit exposure of vulnerable services to untrusted networks. Employing anomaly detection systems to identify unusual crashes or service disruptions related to cryptographic operations can help detect exploitation attempts. For critical systems, consider deploying redundant failover mechanisms to maintain availability in case of crashes. Additionally, vendors and integrators should review their use of mbedtls_asn1_store_named_data and avoid passing inconsistent ASN.1 data structures that could trigger the NULL pointer dereference. Security teams should monitor vendor advisories for patches and apply them promptly. Finally, incorporating fuzz testing and static analysis in development pipelines can help identify similar logic errors in cryptographic code.