CVE-2026-73438 in EOS
Summary
by MITRE • 09/16/2026
On affected platforms running Arista EOS with Open Shortest Path First version 3 (OSPFv3) configured, an unauthenticated attacker on the same OSPFv3 broadcast domain can send a specially crafted set of packets that can cause the Ospf3 agent to restart unexpectedly. The crash results in the loss of all OSPFv3 adjacencies on the affected device and may disrupt routing across the broader OSPF domain until the agent recovers.
This issue was reported externally by Dravanet Inc., and Arista is not aware of any malicious exploitation of this vulnerability in customer networks.
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Analysis
by VulDB Data Team • 09/16/2026
The identified vulnerability affects network infrastructure running Arista EOS with Open Shortest Path First version 3 configured, presenting a significant risk to routing stability within OSPFv3 broadcast domains. An unauthenticated attacker positioned on the same Layer 2 segment as the affected device can exploit this flaw by transmitting specially crafted packets designed to trigger an unexpected restart of the Ospf3 agent process. This denial-of-service condition results in the immediate loss of all OSPFv3 adjacencies maintained by the device, effectively isolating it from its routing peers and disrupting traffic flow across the broader OSPF domain until the service recovers or is manually restarted.
From a technical perspective, this flaw represents a classic input validation failure where the protocol implementation fails to properly sanitize or validate incoming control plane packets before processing them. The vulnerability allows an attacker with local network access to cause a process crash without requiring authentication credentials, highlighting weaknesses in the boundary trust assumptions often present in internal routing protocols. This aligns closely with CWE-20 Improper Input Validation and CWE-400 Uncontrolled Resource Consumption, as the malformed input leads to resource exhaustion or memory corruption that forces the application to terminate unexpectedly. The attack vector is classified under network-based exploitation requiring physical or logical access to the broadcast domain, which corresponds to ATT&CK technique T1498 Network Denial of Service and specifically relates to component-level attacks against routing daemons.
The operational impact of this vulnerability extends beyond simple service interruption for the affected device. Since OSPF is a dynamic link-state routing protocol that relies on continuous neighbor adjacency maintenance, the sudden loss of adjacencies triggers route recalculation across the entire autonomous system. This can lead to temporary black holes in network traffic, increased CPU utilization due to frequent topology changes, and potential instability if multiple devices are affected simultaneously or if recovery mechanisms are slow. Although Arista has noted that there is no evidence of malicious exploitation in customer environments, the ease of execution by an unauthenticated actor on the local segment makes this a high-priority concern for internal network security postures where lateral movement might be attempted to disrupt critical routing infrastructure.
Mitigation strategies should focus primarily on restricting access to OSPFv3 control plane traffic through strict Access Control Lists or firewall rules that limit source IP addresses to known, trusted router interfaces only. Network segmentation is also recommended to isolate management and routing planes from general user broadcast domains where untrusted hosts might reside. Additionally, implementing BGP TTL security mechanisms if applicable, though less relevant for OSPF directly, underscores the importance of protocol hardening features such as MD5 authentication or SHA-HMAC which are supported by Arista EOS and should be enabled to prevent unauthorized packet injection entirely. Regular software updates provided by Arista that address this specific flaw must be applied promptly to restore service resilience against these crafted packet attacks.