CVE-2026-86107 Overview
CVE-2026-86107 is an out-of-bounds write vulnerability [CWE-787] in VeloCloud Edge and Gateway. The flaw exists in the VeloCloud Multipath Protocol (VCMP) tunnel processing logic. Specifically, the vulnerable code path handles tunneled IP fragments exchanged between authenticated overlay neighbors. A successful exploit terminates and restarts the affected process, causing temporary traffic disruption on the VeloCloud SD-WAN fabric. Only authenticated overlay peers can reach the vulnerable logic. Unauthenticated hosts on the internet that cannot establish an overlay peer relationship cannot trigger the condition. Arista published details in Arista Security Advisory #0180.
Critical Impact
An authenticated overlay neighbor can send crafted VCMP-tunneled IP fragments to trigger an out-of-bounds write, restarting the VeloCloud process and disrupting SD-WAN traffic.
Affected Products
- VeloCloud Edge (VCMP tunnel protocol)
- VeloCloud Gateway (VCMP tunnel protocol)
- VMware/Arista VeloCloud SD-WAN deployments processing tunneled IP fragments between overlay neighbors
Discovery Timeline
- 2026-09-16 - CVE-2026-86107 published to NVD
- 2026-09-16 - Last updated in NVD database
Technical Details for CVE-2026-86107
Vulnerability Analysis
The defect resides in the VeloCloud VCMP tunnel protocol handler. VCMP encapsulates traffic between VeloCloud Edges and Gateways across the SD-WAN overlay. When the handler reassembles or processes tunneled IP fragments received from an authenticated peer, it writes past the intended bounds of a destination buffer. The out-of-bounds write [CWE-787] corrupts adjacent memory and causes the packet-processing process to abort. Watchdog logic restarts the process, producing a short traffic outage across the overlay. The condition is bounded to the VCMP tunnel data path; other management or control planes are not affected by this specific issue.
Root Cause
The root cause is missing or incorrect length validation during handling of tunneled IP fragment structures inside a VCMP packet. Reassembly logic trusts fragment offset or length metadata from the peer without confirming that the resulting write remains within allocated buffer boundaries. Because the affected code executes only after the overlay peer relationship is established, exploitation requires possession of valid peer credentials and successful VCMP session formation.
Attack Vector
Exploitation is network-based but constrained. An attacker must be an authenticated overlay neighbor, meaning they must already participate as a peer on the VeloCloud fabric. From that position, the attacker transmits VCMP tunnel packets carrying malformed IP fragments. Processing on the receiving Edge or Gateway crosses the buffer boundary and terminates the process. The impact is availability loss; the advisory does not indicate confidentiality or integrity impact. Attack complexity is high because it depends on overlay peering rather than internet-facing reachability.
No public proof-of-concept code is available. See Arista Security Advisory #0180 for vendor technical details.
Detection Methods for CVE-2026-86107
Indicators of Compromise
- Unexpected restarts or crash logs of the VCMP packet-processing daemon on VeloCloud Edge or Gateway devices.
- Recurring VCMP session resets originating from a specific authenticated overlay peer.
- Short, correlated traffic disruptions across overlay tunnels tied to a single neighbor.
Detection Strategies
- Monitor VeloCloud Edge and Gateway system logs for process termination, watchdog restarts, and core dumps in the VCMP data path.
- Correlate per-peer VCMP fragment counts and reassembly errors to identify malformed fragment activity.
- Alert on repeated overlay tunnel flaps between the same peer pair within short time windows.
Monitoring Recommendations
- Forward VeloCloud Edge and Gateway syslog and SNMP traps to a centralized SIEM for crash and restart telemetry.
- Baseline normal VCMP fragmentation rates per peer and alert on statistical deviations.
- Track overlay peer authentication events to detect unauthorized or unexpected peer additions.
How to Mitigate CVE-2026-86107
Immediate Actions Required
- Apply the fixed VeloCloud Edge and Gateway software versions identified in Arista Security Advisory #0180 as soon as validated in a change window.
- Inventory all overlay peer relationships and remove any peers that are no longer required.
- Rotate or revoke overlay peer credentials suspected of compromise to prevent authenticated exploitation.
Patch Information
Refer to Arista Security Advisory #0180 for the list of fixed VeloCloud Edge and Gateway software versions and upgrade guidance. Arista is the authoritative source for remediation packages covering this VCMP tunnel protocol defect.
Workarounds
- Restrict overlay peering strictly to trusted, managed Edges and Gateways under administrative control.
- Enforce strong authentication and credential hygiene for VCMP peer relationships to reduce the population of hosts that can reach the vulnerable code path.
- Segment management access to VeloCloud Orchestrator so that adversaries cannot introduce new authenticated overlay peers.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.