CVE-2026-86106 Overview
CVE-2026-86106 is a missing authentication vulnerability [CWE-306] affecting Arista Edge units with High Availability (HA) enabled. An unauthenticated actor with network access to the private HA interconnect can trigger sensitive HA peer functions without verification. Successful exploitation results in elevated command execution on affected Edge units.
The vulnerability requires adjacent network access to the private HA interconnect but demands no privileges or user interaction. Arista disclosed the flaw in Security Advisory #0179.
Critical Impact
An attacker with access to the HA interconnect network can invoke privileged peer functions and execute elevated commands on Edge units, compromising confidentiality, integrity, and availability.
Affected Products
- Arista Edge units with High Availability (HA) enabled
- Refer to Arista Security Advisory #0179 for the complete list of affected software versions
Discovery Timeline
- 2026-09-16 - CVE-2026-86106 published to the National Vulnerability Database
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-86106
Vulnerability Analysis
The vulnerability stems from missing authentication on functions exposed over the private HA interconnect. The affected Edge unit trusts inbound requests on this interconnect and processes them as if they originated from a legitimate HA peer. An attacker who reaches this network segment can invoke sensitive peer-facing functions and cause the target unit to run commands with elevated privileges.
The design assumes the HA interconnect is a trusted, isolated network. When that assumption breaks, for example through misconfiguration, lateral movement, or shared VLAN exposure, the lack of peer verification becomes directly exploitable.
Root Cause
The root cause is a missing authentication check on peer-to-peer HA control functions, classified under [CWE-306] Missing Authentication for Critical Function. The service exposed on the HA interconnect does not verify that a caller is an authorized peer before executing privileged operations.
Attack Vector
Exploitation requires adjacent network access to the private HA interconnect, so the attacker must be positioned on the interconnect segment or reach it through a bridged path. From that vantage, the attacker sends crafted requests to HA peer functions and triggers elevated command execution on the target Edge unit without supplying credentials. No user interaction is required. Refer to the Arista Security Advisory #0179 for protocol-level detail.
Detection Methods for CVE-2026-86106
Indicators of Compromise
- Unexpected command execution or configuration changes on Edge units where HA is enabled, with no matching administrator session in audit logs.
- Traffic on the HA interconnect VLAN sourced from MAC or IP addresses that do not belong to the paired HA peer.
- HA peer function invocations occurring outside of expected failover, sync, or health-check windows.
Detection Strategies
- Baseline legitimate HA peer traffic patterns and alert on protocol deviations, unexpected source addresses, or off-cadence peer function calls.
- Correlate Edge unit command execution and configuration change events with authenticated administrator activity to identify unattributed changes.
- Enable and centralize syslog from Arista Edge units, including HA subsystem logs, and monitor for anomalous peer state transitions.
Monitoring Recommendations
- Forward Edge and HA subsystem logs into a centralized analytics platform for cross-device correlation and long-term retention.
- Deploy network monitoring on the HA interconnect segment to detect any device not part of the sanctioned HA pair.
- Alert on new ARP entries, MAC address changes, or unexpected switch port activity on interconnect VLANs.
How to Mitigate CVE-2026-86106
Immediate Actions Required
- Review the Arista Security Advisory #0179 and apply the fixed software version identified for your Edge platform.
- Inventory all Edge units with HA enabled and confirm the HA interconnect is isolated on a dedicated physical link or private VLAN.
- Restrict Layer 2 and Layer 3 reachability to the HA interconnect to the paired peer devices only.
Patch Information
Arista has published remediation guidance in Security Advisory #0179. Consult the advisory for the list of fixed releases and upgrade paths applicable to your Edge platform, then schedule upgrades using standard change control for HA pairs to avoid disrupting failover.
Workarounds
- Physically or logically isolate the HA interconnect so that only the two paired Edge units can communicate on that segment.
- Apply access control lists on adjacent switches to block any traffic to the HA interconnect VLAN that does not originate from a sanctioned peer.
- Audit switch port configurations and remove trunking of the HA VLAN to any port that does not terminate on a paired Edge unit.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
