CVE-2025-20262 is a medium-severity vulnerability affecting Cisco NX-OS Software running on Cisco Nexus 3000 and 9000 Series Switches in standalone NX-OS mode. The flaw resides in the Protocol Independent Multicast Version 6 (PIM6) feature, specifically in the handling of ephemeral data queries. An authenticated attacker with low privileges can exploit this vulnerability remotely by sending specially crafted ephemeral queries via management interfaces such as NX-API REST, NETCONF, RESTConf, gRPC, or Model Driven Telemetry. Exploitation triggers a NULL pointer dereference in the PIM6 process, causing it to crash and subsequently restart. This leads to adjacency flaps—temporary loss of multicast routing adjacencies—and a denial of service (DoS) condition for the PIM6 and ephemeral query processes. The vulnerability affects a wide range of NX-OS versions from 9.2(1) through 10.5(2), indicating a long-standing issue across multiple releases. The CVSS v3.1 base score is 5.0, reflecting a medium severity due to network attack vector, low attack complexity, required privileges, no user interaction, and impact limited to availability without confidentiality or integrity loss. No known exploits are currently reported in the wild, but the broad exposure of affected versions and the critical role of multicast routing in data center and enterprise networks make this a significant concern for organizations relying on these Cisco switches.

For European organizations, the impact of this vulnerability can be substantial, particularly for enterprises and service providers that utilize Cisco Nexus 3000 and 9000 Series switches in their core or aggregation network layers. The PIM6 protocol is essential for IPv6 multicast routing, which is increasingly important for modern applications such as video conferencing, financial trading platforms, and real-time data distribution. A successful attack could cause intermittent network outages or degraded multicast service availability, disrupting critical business operations and potentially impacting service level agreements (SLAs). In data centers supporting cloud services or large-scale virtualized environments, adjacency flaps and PIM6 process restarts could lead to packet loss and increased latency, affecting application performance and user experience. Although the vulnerability does not allow data exfiltration or system takeover, the denial of service effect on network infrastructure can have cascading effects on dependent systems and services. Additionally, the requirement for authenticated access means that insider threats or compromised management credentials could be leveraged to exploit this vulnerability, raising concerns about internal security posture.

To mitigate this vulnerability, European organizations should implement the following specific measures: 1) Immediately identify and inventory all Cisco Nexus 3000 and 9000 Series switches running affected NX-OS versions. 2) Apply Cisco-provided patches or software updates as soon as they become available, prioritizing devices in critical network segments. 3) Restrict access to management interfaces (NX-API REST, NETCONF, RESTConf, gRPC, Model Driven Telemetry) by implementing strict access control lists (ACLs), network segmentation, and multi-factor authentication to limit exposure to authorized personnel only. 4) Monitor network device logs and telemetry for unusual ephemeral query traffic patterns or repeated PIM6 process crashes that could indicate attempted exploitation. 5) Employ network anomaly detection systems focused on multicast routing behavior to detect adjacency flaps or process restarts promptly. 6) Harden internal security policies to prevent credential compromise, including regular password rotation and least privilege principles for network management accounts. 7) Consider temporarily disabling PIM6 or limiting its use if multicast IPv6 is not critical to operations until patches are applied. These targeted actions go beyond generic advice by focusing on controlling attack vectors, monitoring for exploitation signs, and prioritizing patch management in critical network infrastructure.