CVE-2026-30405 is a denial of service vulnerability identified in GoBGP version 4.2.0, an open-source BGP (Border Gateway Protocol) implementation widely used for inter-domain routing on the internet. The vulnerability arises from improper handling of the NEXT_HOP path attribute in BGP update messages. The NEXT_HOP attribute specifies the next hop IP address that should be used to reach a destination network. In this case, a remote attacker can craft malicious BGP update messages with specially manipulated NEXT_HOP attributes that cause the GoBGP daemon (gobgpd) to crash or become unresponsive, leading to a denial of service condition. This disrupts the routing process, potentially causing network outages or degraded performance. Exploitation does not require authentication, but the attacker must be able to send BGP messages to the target router or BGP speaker, which typically implies network-level access or compromised peers. The vulnerability was reserved and published in early March 2026, but no patches or exploits are currently documented. The lack of a CVSS score indicates that the vulnerability is newly disclosed and under evaluation. Given the critical role of BGP in internet routing, this vulnerability poses a significant risk to network stability and availability for organizations relying on GoBGP 4.2.0.

The primary impact of CVE-2026-30405 is a denial of service on network devices running GoBGP 4.2.0, which can lead to loss of routing functionality and network outages. This can disrupt internet connectivity, degrade service quality, and cause cascading failures in dependent systems. Organizations such as ISPs, cloud providers, and enterprises using GoBGP for BGP routing are at risk of service interruptions. The vulnerability could be exploited to selectively disrupt traffic flows or cause widespread outages if leveraged against critical internet infrastructure. The lack of authentication requirement and the ability to trigger the DoS remotely increase the threat level. Although no known exploits exist yet, the potential for attackers to cause significant network disruption is high, especially in environments where GoBGP is deployed at scale or in critical routing roles.

To mitigate CVE-2026-30405, organizations should first verify if they are running GoBGP version 4.2.0 and plan to upgrade to a patched version once available. In the absence of a patch, network administrators should implement strict BGP update filtering to block suspicious or malformed NEXT_HOP attributes from untrusted peers. Deploying prefix and attribute validation techniques such as RPKI (Resource Public Key Infrastructure) can help reduce the risk of malicious BGP updates. Monitoring BGP session stability and routing anomalies can provide early detection of exploitation attempts. Network segmentation and limiting BGP peering to trusted entities reduce exposure. Additionally, implementing rate limiting on BGP update messages and using control-plane protection features can help mitigate the impact of potential attacks. Coordination with upstream providers and sharing threat intelligence can further enhance defense.