CVE-2025-6395 is a vulnerability identified in the GnuTLS library, specifically within the function _gnutls_figure_common_ciphersuite(). The flaw is a NULL pointer dereference, which occurs when the software attempts to access or dereference a pointer that has not been initialized or has been set to NULL. This type of vulnerability can cause the affected application or service to crash, leading to a denial of service (DoS) condition. GnuTLS is a widely used open-source implementation of the TLS (Transport Layer Security) protocol, which provides cryptographic security for network communications. The vulnerability affects Red Hat Enterprise Linux 10, which includes GnuTLS as part of its cryptographic stack. The CVSS v3.1 base score is 6.5, indicating a medium severity level. The vector string (AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H) shows that the attack vector is network-based (AV:N), requires high attack complexity (AC:H), does not require privileges (PR:N) or user interaction (UI:N), and affects availability significantly (A:H) with limited impact on integrity (I:L) and no impact on confidentiality (C:N). There are no known exploits in the wild at the time of publication. The vulnerability could be triggered remotely without authentication, but the complexity of the attack is high, which may limit exploitation. The flaw does not appear to allow code execution or data disclosure but can cause service interruptions by crashing the TLS service or applications relying on GnuTLS, potentially impacting availability of secure communications.

For European organizations, the impact of CVE-2025-6395 primarily revolves around availability disruption of services that rely on GnuTLS for secure communications. This includes web servers, mail servers, VPN gateways, and other networked applications that use Red Hat Enterprise Linux 10 or other distributions incorporating the vulnerable GnuTLS version. A successful exploitation could cause denial of service, interrupting critical business operations, secure communications, and potentially causing downtime for customer-facing services. While the vulnerability does not compromise confidentiality or allow privilege escalation, the loss of availability in security-critical components could degrade trust and operational continuity. Organizations in sectors such as finance, healthcare, government, and critical infrastructure in Europe, which rely heavily on secure TLS communications, may experience operational disruptions. The medium severity rating and high attack complexity suggest that widespread exploitation is less likely, but targeted attacks against high-value or critical infrastructure remain a concern.

To mitigate this vulnerability, European organizations should prioritize applying patches or updates from Red Hat as soon as they become available. Since no patch links are currently provided, organizations should monitor Red Hat security advisories closely. In the interim, administrators can consider the following specific actions: 1) Restrict network access to services using GnuTLS to trusted networks or VPNs to reduce exposure. 2) Implement robust monitoring and alerting for service crashes or unusual TLS handshake failures that may indicate exploitation attempts. 3) Where feasible, temporarily disable or replace GnuTLS-dependent services with alternatives that are not vulnerable or use different TLS libraries until patches are applied. 4) Conduct thorough testing of TLS-dependent applications to identify any abnormal behavior related to TLS handshakes. 5) Employ network-level protections such as rate limiting and intrusion detection systems tuned to detect anomalous TLS traffic patterns. 6) Maintain up-to-date backups and incident response plans to quickly recover from potential denial of service incidents. These steps go beyond generic advice by focusing on reducing attack surface, early detection, and operational continuity.