On affected platforms running Arista EOS with Dynamic Host Configuration Protocol (DHCP) relay configured, an unauthenticated attacker with network access could send a crafted DHCP reply packet from an IP address that is not configured as a helper/destinat
Summary
| CVE | CVE-2026-73437 |
|---|---|
| State | PUBLISHED |
| Assigner | Arista |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-15 22:16:58 UTC |
| Updated | 2026-09-17 04:17:57 UTC |
| Description | On affected platforms running Arista EOS with Dynamic Host Configuration Protocol (DHCP) relay configured, an unauthenticated attacker with network access could send a crafted DHCP reply packet from an IP address that is not configured as a helper address, and the relay agent would forward it to clients without validating the source. This could allow the attacker to supply clients with malicious network configuration parameters, potentially resulting in traffic interception or denial of service for affected clients. |
Risk And Classification
Primary CVSS: v4.0 6.5 MEDIUM from [email protected]
CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.001960000 probability, percentile 0.095250000 (date 2026-09-16)
Problem Types: CWE-345 | CWE-345 CWE-345 Insufficient Verification of Data Authenticity
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | [email protected] | Secondary | 6.5 | MEDIUM | CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H/E:X/C... |
| 4.0 | CNA | CVSS | 6.5 | MEDIUM | CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H |
| 3.1 | [email protected] | Secondary | 9.6 | CRITICAL | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
| 3.1 | CNA | CVSS | 9.6 | CRITICAL | CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
CVSS v4.0 Breakdown
CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CVSS v3.1 Breakdown
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Arista Networks | EOS | affected 4.36.0 4.36.1F custom | 710 Series, 720D Series, 720XP/722XPM Series, 750X Series, 7010TX Series, 7020R/R4 Series, 7130 Series running EOS, 7170 Series, 7050X3/X4 Series, 7060X/X2/X4/X5/X6 Series, 7260X/X3 Series, 7280R/R2/R3/R4 Series, 7300X/X3 Series, 7320X Series, 7358X4 Series, 7368X4 Series, 7388X5 Series, 7500R/R2/R3 Series, 7800R3/R4 Series, 7700R4 Series, AWE 5000 Series, AWE 7200R Series, CloudEOS, cEOS-lab, vEOS-lab, CloudVision eXchange, virtual or physical appliance |
| CNA | Arista Networks | EOS | affected 4.35.0 4.35.5M custom | 710 Series, 720D Series, 720XP/722XPM Series, 750X Series, 7010TX Series, 7020R/R4 Series, 7130 Series running EOS, 7170 Series, 7050X3/X4 Series, 7060X/X2/X4/X5/X6 Series, 7260X/X3 Series, 7280R/R2/R3/R4 Series, 7300X/X3 Series, 7320X Series, 7358X4 Series, 7368X4 Series, 7388X5 Series, 7500R/R2/R3 Series, 7800R3/R4 Series, 7700R4 Series, AWE 5000 Series, AWE 7200R Series, CloudEOS, cEOS-lab, vEOS-lab, CloudVision eXchange, virtual or physical appliance |
| CNA | Arista Networks | EOS | affected 4.34.0 4.34.7.1M custom | 710 Series, 720D Series, 720XP/722XPM Series, 750X Series, 7010TX Series, 7020R/R4 Series, 7130 Series running EOS, 7170 Series, 7050X3/X4 Series, 7060X/X2/X4/X5/X6 Series, 7260X/X3 Series, 7280R/R2/R3/R4 Series, 7300X/X3 Series, 7320X Series, 7358X4 Series, 7368X4 Series, 7388X5 Series, 7500R/R2/R3 Series, 7800R3/R4 Series, 7700R4 Series, AWE 5000 Series, AWE 7200R Series, CloudEOS, cEOS-lab, vEOS-lab, CloudVision eXchange, virtual or physical appliance |
| CNA | Arista Networks | EOS | affected 4.33.0 4.33.9M custom | 710 Series, 720D Series, 720XP/722XPM Series, 750X Series, 7010TX Series, 7020R/R4 Series, 7130 Series running EOS, 7170 Series, 7050X3/X4 Series, 7060X/X2/X4/X5/X6 Series, 7260X/X3 Series, 7280R/R2/R3/R4 Series, 7300X/X3 Series, 7320X Series, 7358X4 Series, 7368X4 Series, 7388X5 Series, 7500R/R2/R3 Series, 7800R3/R4 Series, 7700R4 Series, AWE 5000 Series, AWE 7200R Series, CloudEOS, cEOS-lab, vEOS-lab, CloudVision eXchange, virtual or physical appliance |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| www.arista.com/en/support/advisories-notices/security-advisory/24712-securit... | [email protected] | www.arista.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: This issue was discovered internally by Arista. (en)
Additional Advisory Data
Solutions
CNA: The recommended resolution is to upgrade to a remediated software version at your earliest convenience and enable the reply source-address validation CLI knob under dhcp relay mode: switch(config)# dhcp relay switch(config-dhcp-relay)# reply source-address validation CVE-2026-73437 has been fixed in the following releases: * 4.36.2F and later releases in the 4.36.x train * 4.35.6M and later releases in the 4.35.x train * 4.34.8M and later releases in the 4.34.x train * 4.33.10M and later releases in the 4.33.x train Note: All versions require upgrading to a release containing the fix (as listed above) and applying the required configuration. Arista will not be providing any hotfixes.
Workarounds
CNA: IP locking can be run in a locked address enforcement disabled state, along with the DHCP Relay, to provide protection against rogue DHCP servers and spoofing. This is supported on DHCPv4 starting with EOS-4.29.0F and on DHCPv6 starting with EOS-4.27.0F. For more information, see IP Locking https://www.arista.com/en/support/toi/eos-4-25-1f/14628-ip-locking-release-updates . This is compatible with the following platforms only: * CCS-720XP * CCS-710P * CCS-720DP * CCS-722XPM * DCS-7010TX * DCS-7050CX3 * DCS-7050SX3 * CCS-710XP * CCS-720DF * CCS-720DT * CCS-720XDM * CCS-720XPM * CCS-755 * CCS-758 * DCS-7050CX3M * DCS-7050TX3 * DCS-7304 * DCS-7308 * 7300X3 Untrusted ports can be locked with the following configuration: switch(config)# address locking switch(config-address-locking)# locked-address ipv4 enforcement disabled switch(config-address-locking)# locked-address ipv6 enforcement disabled switch(config)# int et 5 switch(config-if-Et5)# address locking ? ipv4 Enable address locking for IPv4 ipv6 Enable address locking for IPv6 <cr> switch(config-if-Et5)# address locking ipv4 switch(config-if-Et5)# address locking ipv6 The above configuration can be validated using the following output: switch# show address locking IP Locking is active Logging events: None Bindings persistence is enabled Bindings last backup time: Not Available Configured IPv4 Interfaces: Et5 Configured IPv6 Interfaces: Et5 Configured IPv4 VLANs: Configured IPv6 VLANs: Interface Status Interface IPv4 IPv6 ---------------- ---------- ------------------- Ethernet5 yes* yes* * Locked address enforcement is disabled With the above configuration applied, DHCP traffic from untrusted ports can be blocked and the following output reflects the packet drops: switch#show address locking counters detail Action Count --------------------------------- ----- ARP (0.0.0.0) PERMIT 0 DHCP from client to server PERMIT 0 DHCP from server DROP 4 In releases prior to EOS-4.35.0F, “show address locking counters detail” command is not available. Instead, run “show platform trident tcam detail” and grep for these IP Locking counters. switch#show platform trident tcam detail === TCAM detail for switch Linecard0/0 === Groups programmed in IFP ... TCAM group 129 copy 0 in PIPE 0 uses 3 entries and can use up to 12282 more. IP Locking v4 uses 3 entries. 0x0000005c 0 hits - Unknown ARP permit rule 0x0000005d 0 hits - DHCP permit from client 0x00000060 4 hits - DHCP drop from server TCAM group 129 copy 1 in PIPE 0 uses 3 entries and can use up to 12282 more. IP Locking v4 uses 3 entries. 0x0800005c 0 hits - Unknown ARP permit rule 0x0800005d 0 hits - DHCP permit from client 0x08000060 0 hits - DHCP drop from server