CVE-2026-19655: CWE-20 Improper Input Validation in Arista Networks EOS
On affected platforms running Arista EOS with Dynamic Host Configuration Protocol (DHCP) relay/snooping configured with the information option (Option 82), or with the DHCP server configured with match criteria based on the information option, an unauthenticated attacker connected to a client-facing VLAN(s) where the relay is configured can send a specially crafted packet that causes the DHCP Relay service to restart.
AI Analysis
Technical Summary
This vulnerability arises from improper input validation (CWE-20) in Arista EOS DHCP relay/snooping functionality when Option 82 is used. Specifically, if the DHCP relay or server is configured to use Option 82 information or match criteria, an attacker connected to a client-facing VLAN can send a specially crafted DHCP packet that triggers a restart of the DHCP Relay service. This causes a denial of service impacting availability but does not affect confidentiality or integrity.
Potential Impact
The impact is a denial of service (availability) due to the DHCP Relay service restarting unexpectedly. There is no impact on confidentiality or integrity. The attacker does not require privileges or user interaction and must be on a client-facing VLAN where the relay is configured.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a patch is available, restrict access to client-facing VLANs and monitor DHCP relay configurations. No official fix or temporary workaround is provided in the available data.
CVE-2026-19655: CWE-20 Improper Input Validation in Arista Networks EOS
Description
On affected platforms running Arista EOS with Dynamic Host Configuration Protocol (DHCP) relay/snooping configured with the information option (Option 82), or with the DHCP server configured with match criteria based on the information option, an unauthenticated attacker connected to a client-facing VLAN(s) where the relay is configured can send a specially crafted packet that causes the DHCP Relay service to restart.
CVSS v3.1
Score 6.5medium
Affected software
Arista Networks
EOS
pkg:github/aristanetworks/eosRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability arises from improper input validation (CWE-20) in Arista EOS DHCP relay/snooping functionality when Option 82 is used. Specifically, if the DHCP relay or server is configured to use Option 82 information or match criteria, an attacker connected to a client-facing VLAN can send a specially crafted DHCP packet that triggers a restart of the DHCP Relay service. This causes a denial of service impacting availability but does not affect confidentiality or integrity.
Potential Impact
The impact is a denial of service (availability) due to the DHCP Relay service restarting unexpectedly. There is no impact on confidentiality or integrity. The attacker does not require privileges or user interaction and must be on a client-facing VLAN where the relay is configured.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a patch is available, restrict access to client-facing VLANs and monitor DHCP relay configurations. No official fix or temporary workaround is provided in the available data.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Arista
- Date Reserved
- 2026-08-12T18:51:29.572Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6aa9b25a55bf5e2cf55e9557
Added to database: 09/15/2026, 21:02:18 UTC
Last enriched: 09/15/2026, 21:16:56 UTC
Last updated: 09/16/2026, 03:17:50 UTC
Views: 9
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