CVE-2026-30405 is a vulnerability identified in GoBGP gobgpd version 4.2.0, a popular open-source BGP (Border Gateway Protocol) implementation used for routing decisions on the internet and private networks. The flaw resides in the handling of the NEXT_HOP path attribute, a critical component in BGP that specifies the next hop IP address for routing paths. An attacker can craft malicious BGP update messages containing specially manipulated NEXT_HOP attributes that cause the gobgpd daemon to enter a denial of service state, likely by triggering resource exhaustion or a crash (CWE-400). This vulnerability can be exploited remotely without requiring any authentication or user interaction, making it highly accessible to attackers who can reach the BGP session. The CVSS v3.1 base score is 7.5, reflecting a high severity due to its network attack vector, low attack complexity, no privileges required, and no user interaction needed. The impact is limited to availability, with no confidentiality or integrity compromise reported. No patches or fixes have been published at the time of disclosure, and no active exploitation has been observed. Given the critical role of BGP in internet routing, exploitation could disrupt network traffic flow, causing outages or degraded service for affected networks.

The primary impact of CVE-2026-30405 is on the availability of network routing services that rely on GoBGP gobgpd version 4.2.0. Successful exploitation can cause the BGP daemon to crash or become unresponsive, leading to denial of service conditions. This can disrupt routing tables and network traffic flow, potentially causing outages or degraded performance for internet service providers, data centers, cloud providers, and enterprises using GoBGP for BGP routing. The disruption could affect large-scale network infrastructure, impacting end-users and dependent services. Since BGP is foundational to internet routing, instability can propagate and cause broader network issues. The lack of authentication requirements and ease of exploitation increase the risk of attack from remote adversaries. However, the absence of known exploits in the wild and no reported integrity or confidentiality impacts somewhat reduce immediate risk severity. Organizations with exposed BGP sessions or those using vulnerable versions are at significant risk of service disruption.

1. Immediately restrict BGP session access to trusted peers only, using network-level controls such as ACLs and firewall rules to block untrusted IP addresses from establishing BGP connections. 2. Implement prefix filtering and strict validation of BGP update messages to detect and reject malformed or suspicious NEXT_HOP attributes. 3. Monitor BGP daemon logs and network traffic for anomalies indicative of exploitation attempts, such as unexpected crashes or malformed BGP updates. 4. Deploy rate limiting on BGP update messages to reduce the risk of resource exhaustion attacks. 5. Isolate vulnerable GoBGP instances in segmented network zones to limit impact scope. 6. Engage with GoBGP maintainers and subscribe to security advisories for timely patch releases and apply updates promptly once available. 7. Consider deploying redundant BGP routers with failover capabilities to maintain routing availability during an attack. 8. Use BGP session authentication mechanisms (e.g., TCP MD5 signatures) to prevent unauthorized BGP session establishment where possible. 9. Conduct regular security assessments and penetration testing focused on BGP infrastructure to identify and remediate weaknesses proactively.