CVE-2020-3470: Cisco Enterprise NFV Infrastructure RCE Flaw

CVE-2020-3470 Overview

CVE-2020-3470 is a buffer overflow vulnerability in the API subsystem of Cisco Integrated Management Controller (IMC). The flaw allows an unauthenticated, remote attacker to execute arbitrary code with root privileges on the underlying operating system. The root cause is improper boundary checks on user-supplied input passed to the API. An attacker exploits the issue by sending a crafted HTTP request to the API subsystem, triggering an exploitable memory corruption condition. The vulnerability affects a broad range of Cisco UCS C-Series rack servers, Cisco UCS E-Series, Cisco UCS S-Series storage servers, and Cisco Enterprise NFV Infrastructure Software.

Critical Impact
Unauthenticated remote attackers can achieve root-level code execution on the host management controller, providing complete control of affected Cisco UCS hardware platforms.

Affected Products

Cisco Integrated Management Controller (IMC) across UCS C-Series M3, M4, and M5 servers (C125 M5, C220 M5, C240 M5, C480 M5, C480 ML M5, UCS C220 M4, UCS C460 M4, UCS C22/C24/C220/C240/C420 M3)
Cisco UCS E-Series M1, M2, M3 and UCS S3260 / S3160 storage servers
Cisco Enterprise NFV Infrastructure Software and Enterprise Network Compute System 5100 / 5400

Discovery Timeline

2020-11-18 - CVE-2020-3470 published to NVD
2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-3470

Vulnerability Analysis

The vulnerability resides in the API subsystem of the Cisco Integrated Management Controller (IMC), a baseboard management controller embedded in Cisco UCS hardware for out-of-band server management. The IMC exposes an HTTP-based API used for configuration, monitoring, and remote control of the host platform. The vulnerable code paths fail to enforce proper bounds when processing fields contained in incoming HTTP requests. As a result, crafted input can overflow a fixed-size buffer in memory.

Because the IMC processes API requests without prior authentication on the affected paths, exploitation requires only network reachability to the management interface. Successful exploitation yields code execution in the context of the IMC process, which runs with root privileges. Compromise at this layer gives attackers persistent control beneath the host operating system, including the ability to manipulate firmware, KVM sessions, and virtual media.

Root Cause

The defect is classified under [CWE-119] Improper Restriction of Operations within the Bounds of a Memory Buffer and [CWE-20] Improper Input Validation. The API subsystem performs insufficient length validation on user-supplied parameters before copying them into stack or heap buffers. The boundary check failure converts a parsing routine into an exploitable memory corruption primitive.

Attack Vector

Exploitation requires a single crafted HTTP request sent to the IMC API endpoint. No credentials, user interaction, or local access are required. The attack proceeds over the network against any reachable management interface. The vulnerability mechanism is described in Cisco's advisory; no public proof-of-concept exploit code has been released. For technical details refer to the Cisco Security Advisory cisco-sa-ucs-api-rce-UXwpeDHd.

Detection Methods for CVE-2020-3470

Indicators of Compromise

Unexpected outbound connections originating from IMC management IP addresses
Anomalous HTTP POST requests with oversized parameter fields targeting IMC API endpoints
Unauthorized firmware modifications, virtual media mounts, or KVM sessions logged by the IMC
IMC process crashes or unexpected reboots of the management controller without administrative action

Detection Strategies

Inspect network traffic to UCS management interfaces for HTTP requests with abnormally large payloads or malformed parameters
Correlate IMC audit logs with network telemetry to identify API access from unexpected source addresses
Monitor for new administrative accounts or configuration changes on the IMC that do not match approved change tickets

Monitoring Recommendations

Forward IMC syslog and audit events to a centralized SIEM for long-term retention and correlation
Alert on any connection attempts to IMC management ports from networks outside the dedicated out-of-band management VLAN
Track firmware version drift across UCS fleets to surface unauthorized changes that may follow exploitation

How to Mitigate CVE-2020-3470

Immediate Actions Required

Apply the fixed IMC firmware versions identified in the Cisco Security Advisory to every affected UCS C-Series, E-Series, S-Series, and ENCS platform
Restrict access to IMC management interfaces to a dedicated, isolated out-of-band management network
Audit IMC user accounts, certificate trust, and recent configuration changes for signs of tampering
Inventory all Cisco UCS hardware to confirm patch status against the affected CPE list

Patch Information

Cisco released fixed firmware versions for the affected IMC, UCS, ENCS, and Enterprise NFV Infrastructure Software products. Refer to the Cisco Security Advisory cisco-sa-ucs-api-rce-UXwpeDHd for the fixed release table mapped to each hardware generation. No workarounds were published by Cisco; patching is the only supported remediation.

Workarounds

No vendor-supplied workarounds exist; reduce exposure by placing IMC interfaces on a dedicated management VLAN reachable only by authorized administrators
Enforce ACLs on upstream switches and firewalls to block all HTTP/HTTPS traffic to IMC addresses from production and user networks
Disable unused IMC services and interfaces where operationally feasible until firmware updates are applied

bash

# Example: restrict access to IMC management subnet using an ACL on an upstream Cisco device
ip access-list extended IMC-MGMT-ACL
 permit tcp host 10.10.250.10 10.20.30.0 0.0.0.255 eq 443
 permit tcp host 10.10.250.11 10.20.30.0 0.0.0.255 eq 443
 deny   tcp any 10.20.30.0 0.0.0.255 eq 443
 deny   tcp any 10.20.30.0 0.0.0.255 eq 80
 permit ip any any
!
interface Vlan30
 ip access-group IMC-MGMT-ACL in