CriticalCVE-2026-7473

Arista EOS Unexpected Tunnel Protocol Decapsulation and Forwarding Bypass (CVE-2026-7473)

Published 05.06.2026Last modified 25.10.2026In CISA KEV since 09.06.2026Sources: CVE.org, pwn.watch

What is affected, what to do

On affected platforms running Arista EOS where a tunnel decapsulation configuration—such as VXLAN (Virtual Extensible LAN), decap-groups, or a GRE (Generic Routing Encapsulation) tunnel interface—is present, the switch will incorrectly decapsulate and forward other unexpected tunneled packet with a destination IP matching its configured decapsulation IP. This occurs because the switch does not verify the tunnel protocol type, potentially leading to the unexpected processing of non-configured tunnel traffic.

The vulnerability is being actively exploited; treat it as a priority. The available sources name no fixed version. Check the vendor guidance in the references below. Immediate actions, mitigation and detection rules are in the runbook below.

Affected: Arista Networks EOS eq 4.36.0..4.36.0
Arista Networks EOS lte 4.35.0..4.35
Arista Networks EOS lte 4.34.0..4.34
Arista Networks EOS lte 4.33.0..4.33
Arista Networks EOS lte 4.32.0..4.32
Arista Networks EOS lte 4.31.0..4.31
Arista Networks EOS lte *..4.30

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Metrics

6.9

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: NVD, CVSS v4

5.8

CVSS v3

Severity Medium on the scale from 0 to 10.

Source: CVE.org, pwn.watch

1.1 %

EPSS score

Moderate — model estimates 1-10% exploitation likelihood.

Source: FIRST EPSS, percentile 65.8

Show all metrics

Severity: Critical
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 187.55 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 6.9 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 5.8
CVSS v4 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 6.9
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 1.1 %; Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 65.8; High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: Actively exploited
Published: 05.06.2026
In CISA KEV since The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: 09.06.2026
CISA assessment (SSVC): Exploitation: active · automatable · Technical impact: total; Source: CISA Vulnrichment, as of 10 June 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-1023

Response and mitigation

Why act now?

Prioritisation rationale

The flaw is network-reachable without authentication and has a changed scope. An attacker can craft a mismatched tunnel to slip packets past perimeter ACLs straight into internal segments or VRFs. The impact is on the integrity of segmentation rather than on availability or direct data theft. Typical targets are data-centre fabrics, border leafs, DCI links and provider edges running VXLAN or GRE. CISA reports no known ransomware use, and the statistical exploitation likelihood is only moderate, but the KEV listing confirms real-world abuse. Treat it as high priority (patch or iACL within 24 h) wherever decap IPs are reachable from the internet or third-party networks. For a strictly internal, well-isolated underlay, medium priority in the regular maintenance window is sufficient.

01
Runbook step 1
Immediate response (0-24 h)
- Scope the estate: Inventory every Arista EOS device with show version. Affected trains are 4.30 through 4.36.0. Then narrow the list with show running-config | section vxlan|decap-group|interface Tunnel. Only devices with a tunnel decapsulation configuration (VXLAN, decap-groups or GRE tunnel interfaces) are exploitable.
- Patch: A fix is available from the vendor. Look up the fixed EOS release in the Arista Security Advisory for CVE-2026-7473. Upgrade border leafs and spines whose decap IPs are externally reachable first, using ISSU or MLAG maintenance windows.
- Enumerate decap IPs: Record the VTEP loopback (interface Vxlan1 → vxlan source-interface), decap-group addresses (show ip decap-group) and GRE tunnel sources (show interfaces Tunnel). Then confirm whether any of them is reachable from the internet, partner networks or untrusted VRFs.
- Emergency edge ACL: Block traffic to all decap IPs from untrusted sources for IP protocols 47 (GRE), 4 (IP-in-IP) and 41 (6in4), and for UDP 4789 (VXLAN), UDP 6081 (GENEVE) and UDP 6635 (MPLS-over-UDP). Permit only known tunnel peers.
- Check routing exposure: Make sure VTEP and tunnel loopbacks are not leaked into external BGP sessions or other tenants' routing tables. Tighten route-maps and prefix-lists immediately where needed.
02
Runbook step 2
Mitigation layers
- Network segmentation / infrastructure ACL: Apply an iACL on fabric-edge ingress interfaces. Per decap IP, it permits only the configured tunnel protocol from defined peers and drops everything else with logging. Examples: deny gre any host <VTEP-IP> log, permit udp <VTEP-peer-net> host <VTEP-IP> eq 4789, deny ip any host <VTEP-IP> log.
- Per-device protocol pinning: If a switch should only terminate VXLAN, explicitly drop GRE and IP-in-IP to its VTEP IP. Apply the same logic in reverse for GRE-only endpoints. The ACL compensates for the missing protocol-type check in the switch.
- Anti-spoofing: Enable uRPF (ip verify unicast source reachable-via rx) on external interfaces and enforce BCP38 filtering. This stops outsiders from injecting tunnel packets sourced from underlay or internal addresses.
- Underlay isolation: Keep the underlay (loopbacks, P2P links) in a dedicated VRF or address space that is not routable from overlay tenants or management networks.
- Configuration hygiene: Remove unused decap-groups and GRE tunnel interfaces. Every unnecessary decap configuration widens the attack surface.
- Downstream controls: Do not let east-west firewalls or microsegmentation assume that overlay traffic only originates from legitimate tunnels. Keep those rules restrictive.
03
Runbook step 3
Detection rules
- sFlow/IPFIX from the Arista device: Look for flows to a decap IP using a protocol that does not match its configuration, such as GRE to a VXLAN VTEP. SPL example: index=netflow dest_ip IN (<vtep_ips>) (protocol=47 OR protocol=4 OR protocol=41 OR dest_port=6081) NOT src_ip IN (<known_peers>)
- Zeek tunnel analysis: In tunnel.log, alert on entries with tunnel_type in {Tunnel::GRE, Tunnel::IP, Tunnel::VXLAN, Tunnel::GENEVE} where the destination is a decap IP and the source is not a known peer. Tunnels sourced from internet addresses are also suspicious.
- ACL logging (syslog): Correlate hits on the deny … log entries above in the SIEM. Repeated hits from a small set of external sources indicate active probing. Rule idea: more than 5 hits per source in 10 minutes.
- Inner-packet anomalies: Use Suricata or NDR behind the fabric to find traffic whose source addresses appear in segments where they cannot topologically exist. Examples are internal RFC1918 sources with no matching ARP or MAC-learning events, or unexpected destinations in server VLANs.
- Device counters: Trend show interfaces Vxlan1 counters, show interfaces Tunnel<n> and decap-group statistics. A rise in decapsulated packets without a matching rise in legitimate overlay sessions is a red flag.

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

Source: NVD (NIST), pwn.watch, cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
Arista Networks	EOS	`4.35.0 – ≤ 4.35` `4.34.0 – ≤ 4.34` `4.32.0 – ≤ 4.32` `≤ 4.30` `4.31.0 – ≤ 4.31` `4.36.0` `4.33.0 – ≤ 4.33`	— — — — — — —

Vendors and products

Affected operating systems

Affected operating systems

Other	arista	eos	—

Weakness classes (CWE)

CWE-1023Incomplete Comparison with Missing Factors
Class
The product performs a comparison between entities that must consider multiple factors or characteristics of each entity, but the comparison does not include one or more of these factors.
Entry at MITRE CWE-1023

Public exploit references

Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

Public exploit references

CISA KEV Catalog	CISA Known Exploited Vulnerability (opens in a new tab)cisa.gov	actively exploited	09.06.2026
PoC-in-GitHub (nomi-sec)	CVE-2026-7473---Arista-EOS-Tunnel-Decapsulation-Bypass (opens in a new tab)github.com	PoC (publicly reported)reported, not verified	11.06.2026

References & sources

arista.comen/support/advisories-notices/security-advisory/22872-security-…Vendor advisory, Broken link
arista.comArista Extensible Operating System — CVE-2026-7473Vendor advisory, pwn-watch, Mitigation, Vendor advisory
cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2026-7473government-resource, US government resource
pwn.watchpwn.watch: Arista Extensible Operating System: Arista Extensible Operating System Incomplete Comparison with Missing Factors Vulnerabilitypwn-watch
NVD (NIST)NVD: CVE-2026-7473pwn-watch
cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

07.10.2026Record modifiedarista.com

New references:

https://www.arista.com/en/support/advisories-notices/security-advisory/22872-security-advisory-0137

Show 3 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://www.arista.com/en/support/advisories-notices/security-advisory/22872-security-advisory-0137
Reference	removed	https://www.arista.com/en/support/advisories-notices/security-advisory/22872-security-advisory-0137	—
Reference type	removed	https://www.arista.com/en/support/advisories-notices/security-advisory/22872-security-advisory-0137 Types: Broken Link	—

Source identifier: psirt@arista.com

07.10.2026Record modifiedCISA ADP

CISA assessment (SSVC): exploitation: active, automatable: yes

New references:

Show 8 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://www.arista.com/en/support/advisories-notices/security-advisory/24005-security-advisory-0137
Reference	added	—	https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-7473
Reference	removed	https://www.arista.com/en/support/advisories-notices/security-advisory/24005-security-advisory-0137	—
Reference	removed	https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-7473	—
Reference type	removed	https://www.arista.com/en/support/advisories-notices/security-advisory/24005-security-advisory-0137 Types: Mitigation, Vendor Advisory	—
Reference type	removed	https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-7473 Types: US Government Resource	—
SSVC assessment	removed	{"id":"CVE-2026-7473","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-06-08T00:00:00+00:00"}	—
SSVC assessment	added	—	{"id":"CVE-2026-7473","role":"CISA Coordinator","options":[{"exploitation":"active"},{"automatable":"yes"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-06-10T03:57:42.438072Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

08.06.2026Record modifiedCISA ADP
New references:
- https://www.arista.com/en/support/advisories-notices/security-advisory/24005-security-advisory-0137
Show the original change
Individual changes of this event as published by NVD
Type Action Before After
Reference added
—
https://www.arista.com/en/support/advisories-notices/security-advisory/24005-security-advisory-0137
Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

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What is affected, what to do

Metrics

Response and mitigation

Prioritisation rationale

Immediate response (0-24 h)

Mitigation layers

Detection rules

Detection rules

Classification under NIS2 and CRA

Description

Affected products

Vendors and products

Affected operating systems

Weakness classes (CWE)

Public exploit references

References & sources

Changes to this CVE