CISCO Security Advisory
Published Date: Not specified
CVE: CVE-2026-20212
Advisory Summary
💠Title: Cisco Nexus 9000 Series — Silicon One RCE (Critical)
An unauthenticated remote code execution (RCE) vulnerability has been identified in the Silicon One integration for Cisco Nexus 9000 Series switches. A threat actor may be able to execute commands with root privileges by sending crafted input to exposed service ports.
- Attack is remote and unauthenticated: No valid credentials are required.
- Privilege level: Successful exploitation can lead to root-level code execution.
- Operational impact: Exploitation may also cause the S1HAL process to crash, potentially triggering a device reload—creating risk of downtime and control-plane instability.
- The vulnerability is tied to TCP ports 43210 and 43211 being accessible in the default L3 VRF (Layer 3 Virtual Routing and Forwarding).
- Exposure of those ports effectively increases the reachable attack surface from networks that can reach the switch.
- ✅ Apply Cisco’s released software updates addressing this vulnerability (recommended).
- 🧷 Use available workarounds if immediate patching isn’t possible—typically focused on restricting network access to the affected ports/services (e.g., VRF reachability and ACLs/firewalling strategies aligned to your network design).
- CVE-2026-20212
- Severity: Critical
- Confirm whether TCP 43210/43211 are reachable from any untrusted segment.
- Validate firewall/ACL posture for the default L3 VRF path(s) to the Silicon One components.
- Check fleet-wide device versions and determine patch windows for affected Nexus 9000 deployments.
- High likelihood of exploitation where management/telemetry integrations are reachable across flatter network zones.
- Potential for both full compromise (root RCE) and availability disruption (S1HAL crash/reload), making this more than a “configuration-only” exposure.
- Customers relying on Silicon One-driven workflows should treat this as a priority remediation event comparable to other critical edge-to-control plane risks.
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-2026-20212
Reference: Vendor Advisory