CVE-2025-6395 is a vulnerability identified in the GnuTLS cryptographic library, specifically within the _gnutls_figure_common_ciphersuite() function. This flaw manifests as a NULL pointer dereference, which occurs when the software attempts to access or manipulate memory through a pointer that has not been properly initialized or has been set to NULL. The consequence of this dereference is typically a crash of the affected application, leading to a denial of service (DoS) condition. The vulnerability affects Red Hat Enterprise Linux 10, which bundles GnuTLS as part of its cryptographic and TLS/SSL support stack. According to the CVSS 3.1 vector, the attack vector is network-based (AV:N), requiring no privileges (PR:N) or user interaction (UI:N), but with high attack complexity (AC:H). The impact on confidentiality is none (C:N), integrity is low (I:L), and availability is high (A:H), indicating that while data confidentiality is not compromised, the ability to maintain service availability can be significantly affected. No known exploits have been reported in the wild, suggesting that exploitation may be difficult or not yet weaponized. The vulnerability was published on July 10, 2025, and no patches or mitigations were listed at the time of this report. The flaw likely arises during the negotiation of common cipher suites between client and server, where an unexpected or malformed input causes the NULL pointer dereference. This vulnerability could be triggered remotely by an attacker sending crafted TLS handshake messages to a vulnerable service using GnuTLS, causing it to crash and disrupt service.

For European organizations, the primary impact of CVE-2025-6395 is the potential for denial of service attacks against systems running Red Hat Enterprise Linux 10 with the vulnerable GnuTLS library. This could disrupt critical services that rely on TLS for secure communications, including web servers, VPN gateways, and other networked applications. While the vulnerability does not expose sensitive data or allow unauthorized data modification, the loss of availability can affect business continuity, especially in sectors such as finance, healthcare, and government where uptime is critical. Organizations with automated systems or embedded devices using Red Hat Enterprise Linux 10 might experience unexpected service interruptions. The high attack complexity reduces the likelihood of widespread exploitation, but targeted attacks against high-value infrastructure remain a concern. The absence of known exploits in the wild currently lowers immediate risk but does not eliminate the threat, especially as attackers may develop exploits over time. Additionally, denial of service conditions could be used as a distraction or part of multi-stage attacks. The impact is more pronounced in environments where redundancy and failover mechanisms are insufficient to mitigate service disruptions.

To mitigate CVE-2025-6395, European organizations should prioritize applying official patches from Red Hat as soon as they become available. In the interim, organizations can reduce exposure by restricting network access to services using GnuTLS, particularly limiting incoming TLS handshake requests from untrusted sources. Monitoring logs and system behavior for abnormal crashes or service restarts related to TLS communications can help detect attempted exploitation. Employing network-level protections such as intrusion detection/prevention systems (IDS/IPS) configured to identify malformed TLS handshake attempts may provide additional defense. Where feasible, organizations should consider upgrading to newer versions of Red Hat Enterprise Linux or alternative cryptographic libraries not affected by this vulnerability. Implementing redundancy and failover strategies can minimize the impact of potential denial of service conditions. Security teams should also review and update incident response plans to address potential service outages caused by this vulnerability. Finally, maintaining up-to-date asset inventories to identify all systems running vulnerable GnuTLS versions is critical for comprehensive mitigation.