CVE-2026-7473

Description

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. This issue has been reported as being exploited in the wild.

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

• 5.8CVSS 3.1, Mediumfrom the CNA (Arista)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N
• 6.9CVSS 4.0, Mediumfrom the CNA (Arista)CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N

What to do

• 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 detailed in the workaround block.CNA solution statement
• There are two broad approaches to mitigate this issue - (1) applying ACLs on upstream devices or (2) applying ACLs on the devices where the unexpected decapsulation is happening. In both cases, the idea is to either selectively allow only legitimate tunnel traffic or to selectively block malicious tunnel traffic. For example, if a network is configured to forward VXLAN traffic, but GRE traffic is being unexpectedly forwarded, then ACLs can be used to either selectively allow just VXLAN traffic or selectively block GRE traffic. More details about using the ACL feature can be found in the  Arista User Manual https://www.arista.com/en/um-eos/eos-acls-and-route-maps#xx1150869 . A note of caution, the following ACL-based mitigation recommendations assume that the tunnel IP is dedicated solely to receiving the configured tunnel protocol traffic. When adapting these rules for your environment, it is important to explicitly permit any additional protocol traffic—such as BGP or SSH—if that IP serves multiple functions. To maintain connectivity, ensure these permit statements are sequenced before any deny statements directed at the decapsulation IP. The following configurations align with the recommendations outlined in the  Arista EOS Hardening Guide https://arista.my.site.com/AristaCommunity/s/article/arista-eos-hardening-guide#Comm_Kna_ka0Uw00000097VJIAY_71 .CNA workaround statement
• Approach 1 - Applying ACL on Upstream Switches On upstream devices, applying ACLs to allow specific tunneled traffic is straightforward. ACLs can be applied that match on tunnel destination IP, the IP next protocol field, and (optionally) UDP destination port to selectively allow or block specific tunnel protocols. Example ACLs for Arista EOS follows. ACL to permit VXLANv4 Only This IPv4 ACL matches on VXLAN packets as follows: (a) IP next protocol = UDP (17) (b) IP DIP = VXLAN VTEP IP (c) UDP destination port = VXLAN UDP Port (4789) It allows VXLAN packets and drops all other packets to the VXLAN Decap IP. ip access-list foo    counters per-entry    1 permit udp any host <vxlan-decap-ip> eq 4789    2 deny ip any host <decap-ip>    3 permit ip any any   ACL to permit GREv4 Only This IPv4 ACL matches on GRE packets as follows: (a) IP next protocol = GRE (47) (b) IP DIP = GRE Tunnel Destination IP It allows GRE packets and drops all other packets to the GRE Decap IP. ip access-list foo    counters per-entry    1 permit gre any host <gre-decap-ip>    2 deny ip any host <gre-decap-ip>    3 permit any any   ACL to permit IP-in-IPv4 Only This IPv4 ACL matches on IP-in-IPv4 packets as follows: (a) IP next protocol = IPv4 (4) or IPv6 (41) (b) IP DIP = IP-in-IP Decap IP It allows IP-in-IPv4 packets and drops all other packets to the IP-in-IPv4 Decap IP. ip access-list foo    counters per-entry    1 permit 4 any host <ipip-decap-ip>    2 permit 41 any host <ipip-decap-iCNA workaround statement
• Approach 2 - Applying ACL on Decapsulation Switches Applying ACLs on the decapsulation device is more complicated. It requires the use of MAC ACLs on 7020R Series, 7280R/R2 Series, and 7500R/R2 Series systems and IP ACLs on 7280R3 Series, 7500R3 Series, and 7800R3 Series systems. In both cases, a TCAM profile update is also required. Note that TCAM profile update is a disruptive operation that could impact traffic forwarding. More information can be found in  User-defined TCAM Profiles https://www.arista.com/en/support/toi/eos-4-26-0f/14755-user-defined-tcam-profiles . 7020R Series, 7280R/R2 Series, and 7500R/R2 Series Mitigation involves using MAC ACLs to allow specific expected protocol packets and block all other traffic to the configured decap IPs. The suggested MAC ACLs use User Defined Fields (UDFs) to match on specific fields in the packet headers. This requires a TCAM profile update to include the following UDF qualifiers: * For IPv4 tunnels, 2 16b and 1 32b UDF qualifiers need to be included. * For IPv6 tunnels, 2 16b and 4 32b UDF qualifiers need to be included. However, in order to make room for the UDF qualifiers, other TCAM features/qualifiers must be removed due to hardware constraints. Following are some suggested TCAM profile changes to accommodate the required UDF qualifiers: * TCAM profile that includes the UDF qualifiers for IPv4 tunnels, but removes support for MPLS: hardware tcam    profile test copy default       feature acl port mac          no kCNA workaround statement
• ACL to permit VXLAN v4 Decap only This MAC ACL uses UDF to match on VXLAN packets as follows: (a) IP next protocol = UDP (0x11) (b) IP DIP = VXLAN VTEP IP (say 0xXXXXXXXX - converted in hex) (c) UDP destination port = VXLAN UDP Port (0x12b5) It allows VXLAN packets and drops all other packets to the VXLAN Decap IP. mac access-list payload alias ip-next-protocol-udp offset 2 pattern 0x00110000 mask 0xff00ffff mac access-list payload alias ip-dip-decap-ip offset 4 pattern 0xXXXXXXXX mask 0x00000000      mac access-list payload alias udp-dport-vxlan offset 5 pattern 0x000012b5 mask 0xffff0000      mac access-list foo    counters per-entry    1 permit any any ip payload alias ip-next-protocol-udp alias ip-dip-decap-ip alias udp-dport-vxlan    2 deny any any ip payload alias ip-dip-decap-ip    3 permit any any   ACL to permit GREv4 Decap Only This MAC ACL uses UDF to match on GRE packets as follows: (a) IP next protocol = GRE (0x2f) (b) IP DIP = GRE Decap IP (say 0xXXXXXXXX - converted in hex) It allows GRE packets and drops all other packets to the GRE Decap IP. mac access-list payload alias ip-next-protocol-gre offset 2 pattern 0x002f0000 mask 0xff00ffff mac access-list payload alias ip-dip-decap-ip offset 4 pattern 0xXXXXXXXX mask 0x00000000 mac access-list foo    counters per-entry    1 permit any any ip payload alias ip-next-protocol-gre alias ip-dip-decap-ip    2 deny any any ip payload alias ip-dip-decap-ip    3 permit any any   If needed, the ACL can also be tCNA workaround statement
• ACL to permit IP-in-IPv4 Decap Only This MAC ACL uses UDF to match on IP-in-IP packets as follows: (a) IP next protocol = IPv4 (0x04) or IPv6 (0x29) (b) IP DIP = IP-in-IP Decap IP (say 0xXXXXXXXX - converted in hex) It allows IP-in-ip packets and drops all other packets to the IP-in-IP Decap IP. mac access-list payload alias ip-next-protocol-ipv4 offset 2 pattern 0x00040000 mask 0xff00ffff mac access-list payload alias ip-next-protocol-ipv6 offset 2 pattern 0x00290000 mask 0xff00ffff mac access-list payload alias ip-dip-decap-ip offset 4 pattern 0xXXXXXXXX mask 0x00000000 mac access-list foo    counters per-entry    1 permit any any ip payload alias ip-next-protocol-ipv4 alias ip-dip-decap-ip     2 permit any any ip payload alias ip-next-protocol-ipv6 alias ip-dip-decap-ip    3 deny any any ip payload alias ip-dip-decap-ip    4 permit any any   ACL to permit GUEv4 Decap Only This MAC ACL uses UDF to match on GUE packets as follows: (a) IP next protocol = UDP (0x11) (b) IP DIP = GUE Decap IP (say 0xXXXXXXXX - converted in hex) (c) UDP destination port = UDP port configured per payload       (say UDP port for IP payload = 0xYYYY or UDP port for MPLS payload = 0xZZZZ - converted in hex) It allows GUE packets and drops all other packets to the GUE Decap IP. mac access-list payload alias ip-next-protocol-udp offset 2 pattern 0x00110000 mask 0xff00ffff mac access-list payload alias ip-dip-decap-ip offset 4 pattern 0xXXXXXXXX mask 0x00000000 mac access-list payload aliasCNA workaround statement
• Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

CAPEC-272 Protocol Abuse (CNA impact statement)

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

CNA context is abbreviated; consult the original record for the complete statements.

Read the original CVE record.

Affected products

Timeline

1. 5 Jun 2026 Published
2. 9 Jun 2026 Added to the CISA KEV catalogue

Weakness

• CWE-1023

References

• www.arista.comvendor-advisory