Hackers have been exploiting a vulnerability in Arista Extensible Operating System (EOS) as a zero-day that will not be patched.
Arista EOS is a modular, Linux-based network operating system designed for the vendor’s high-performance switches for data center, cloud, and enterprise environments.
Tracked as CVE-2026-7473 (CVSS score of 6.9), the security defect exists because, in certain configurations, the tunnel protocol type is not verified, potentially leading to non-configured tunnel traffic being processed.
The flaw can be triggered only on devices running Arista EOS that have been configured as a tunnel endpoint with a decapsulation IP, such as decap-groups, a GRE (Generic Routing Encapsulation) tunnel interface, or VXLAN (Virtual Extensible LAN).
“A device configured to decapsulate one tunnel type will also incorrectly accept and decapsulate other tunnel protocols destined to the same IP address, even if those protocols were not explicitly configured,” Arista explains.
