CVE-2025-61102 is a security vulnerability identified in the FRRouting (FRR) software suite, specifically affecting versions from 4.0 through 10.4.1. The flaw exists in the show_vty_ext_link_adj_sid function located in the ospf_ext.c source file, where a NULL pointer dereference can occur. This vulnerability can be exploited by sending a specially crafted OSPF (Open Shortest Path First) packet to the affected FRRouting instance. When triggered, the NULL pointer dereference leads to a Denial of Service (DoS) condition by crashing the FRRouting daemon or causing it to become unstable, thereby disrupting OSPF routing operations. OSPF is a widely used interior gateway protocol in enterprise and service provider networks for dynamic routing. FRRouting is an open-source routing software suite commonly deployed on network devices and servers to manage routing protocols including OSPF. The vulnerability does not require authentication or user interaction, making it easier for remote attackers to exploit if they can send OSPF packets to the target. Currently, there are no known public exploits or patches available, and no CVSS score has been assigned. The impact is primarily on availability, as the attack disrupts routing services, potentially causing network outages or degraded performance. The vulnerability highlights the importance of validating input packets and robust error handling in routing protocol implementations. Organizations using FRRouting in their network infrastructure should monitor for suspicious OSPF traffic and prepare to apply patches once released.

The primary impact of CVE-2025-61102 is a Denial of Service condition affecting network availability by crashing or destabilizing the FRRouting daemon handling OSPF routing. For European organizations, this could lead to significant network outages, especially in environments relying heavily on FRRouting for dynamic routing such as ISPs, data centers, and large enterprises. Disrupted OSPF routing can cause loss of connectivity between network segments, impacting business-critical applications and services. The vulnerability could be exploited remotely without authentication, increasing the risk of widespread disruption if exposed to untrusted networks. Given the importance of network availability in sectors like finance, telecommunications, and government, the DoS could have cascading effects on operational continuity and service delivery. Additionally, the lack of current patches means organizations must rely on network-level mitigations, which may not fully prevent exploitation. The impact is heightened in multi-tenant or cloud environments where FRRouting is used for tenant isolation and routing, potentially affecting multiple customers. Overall, the vulnerability poses a high risk to network stability and service availability in European infrastructures using FRRouting.

To mitigate CVE-2025-61102, organizations should implement the following specific measures: 1) Monitor and restrict OSPF traffic sources by configuring access control lists (ACLs) or firewall rules to allow OSPF packets only from trusted routers and network segments, minimizing exposure to crafted packets from untrusted sources. 2) Employ network segmentation to isolate routing protocol traffic from general user traffic, reducing the attack surface. 3) Enable logging and anomaly detection for OSPF packets to identify unusual or malformed packets that could indicate exploitation attempts. 4) Prepare for rapid deployment of vendor patches or updates once they become available by maintaining an up-to-date inventory of FRRouting instances and their versions. 5) Consider deploying redundant routing paths and failover mechanisms to maintain network availability in case of a DoS event. 6) Conduct regular security assessments and penetration testing focused on routing protocols to identify and remediate weaknesses proactively. 7) If possible, temporarily disable or limit OSPF on interfaces exposed to untrusted networks until patches are applied. These targeted actions go beyond generic advice by focusing on controlling OSPF traffic and preparing for patch management specific to FRRouting deployments.