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.
According to the company, the security defect impacts 7020R, 7280R/R2, and 7500R/R2 series products. Certain IP-in-IPv6 and GUE IPV6 decap group scenarios apply to 7280R3, 7500R3, and 7800R3 series devices.
“This issue has been reported as being exploited in the wild,” Arista notes in a May advisory.
The company has provided detailed mitigation instructions, but noted that no patches or hotfixes will be released to address the vulnerability.
“No software upgrade path is planned to address this issue due to the risk of breaking existing configuration on deployments. The recommended resolution of this issue is to follow the appropriate mitigation instructions,” Arista says.
On Tuesday, the US cybersecurity agency CISA added CVE-2026-7473 to its Known Exploited Vulnerabilities (KEV) list, urging federal agencies to address it within two weeks.
CISA also expanded its KEV list to include two recently disclosed flaws, one in Chrome (CVE-2026-11645) and another in Cisco SD-WAN (CVE-2026-20245), both of which have been exploited in the wild as zero-days.
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