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

CVE-2020-3470 Overview

Multiple vulnerabilities in the API subsystem of Cisco Integrated Management Controller (IMC) could allow an unauthenticated, remote attacker to execute arbitrary code with root privileges. The vulnerabilities are due to improper boundary checks for certain user-supplied input. An attacker could exploit these vulnerabilities by sending a crafted HTTP request to the API subsystem of an affected system. When this request is processed, an exploitable buffer overflow condition may occur. A successful exploit could allow the attacker to execute arbitrary code with root privileges on the underlying operating system (OS).

Critical Impact

Unauthenticated remote attackers can achieve complete system compromise with root-level access through buffer overflow exploitation in the IMC API subsystem, affecting a wide range of Cisco UCS server platforms and enterprise infrastructure.

Affected Products

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

Discovery Timeline

• November 18, 2020 - CVE-2020-3470 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2020-3470

Vulnerability Analysis

This vulnerability chain targets the API subsystem of Cisco Integrated Management Controller, a critical component used for out-of-band server management across Cisco's enterprise hardware portfolio. The fundamental issue lies in improper boundary checks when processing user-supplied input within API request handlers.

The IMC provides administrators with remote hardware management capabilities including power control, firmware updates, and system monitoring. Because IMC operates independently of the host operating system, successful exploitation grants attackers persistent access that survives host OS reboots and reimaging.

The weakness types associated with this vulnerability (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer and CWE-20: Improper Input Validation) indicate that the API subsystem fails to properly validate and constrain input data before processing it in memory operations.

Root Cause

The root cause stems from improper boundary checks for user-supplied input within the IMC API subsystem. When the API processes incoming HTTP requests, insufficient validation of input parameters allows attackers to supply malformed data that exceeds expected buffer boundaries. This improper input validation (CWE-20) leads to memory corruption conditions (CWE-119) that can be exploited for arbitrary code execution.

The API endpoints exposed for management functions do not adequately sanitize or constrain the length and content of request parameters before copying them into fixed-size memory buffers. This classic buffer overflow pattern allows attackers to overwrite adjacent memory structures and gain control of program execution flow.

Attack Vector

The attack vector is network-based, requiring no authentication or user interaction. An attacker with network access to the IMC management interface can craft malicious HTTP requests targeting vulnerable API endpoints.

The exploitation process involves:

1. Reconnaissance: The attacker identifies systems with exposed IMC management interfaces on the network
2. Request Crafting: A specially crafted HTTP request is constructed with oversized or malformed parameters designed to trigger the buffer overflow condition
3. Memory Corruption: When the vulnerable API endpoint processes the malicious request, the buffer overflow corrupts memory structures
4. Code Execution: The attacker leverages the memory corruption to redirect execution to attacker-controlled code with root privileges

Since no code examples are available from verified sources, administrators should review the Cisco Security Advisory for detailed technical information about the affected API endpoints and exploitation mechanics.

Detection Methods for CVE-2020-3470

Indicators of Compromise

• Unexpected or malformed HTTP requests to IMC API endpoints containing unusually long parameter values
• Anomalous process activity or crashes within the IMC management subsystem
• Unauthorized changes to IMC configuration or firmware
• New or modified user accounts in the IMC administrative interface
• Unexpected outbound network connections originating from the IMC management network segment

Detection Strategies

• Deploy network intrusion detection signatures to identify malicious HTTP requests targeting known vulnerable IMC API endpoints
• Monitor IMC system logs for abnormal API access patterns, authentication failures, or service crashes
• Implement deep packet inspection on management network traffic to detect buffer overflow attack patterns
• Use SentinelOne's network detection capabilities to identify reconnaissance and exploitation attempts against management interfaces

Monitoring Recommendations

• Establish baseline network traffic patterns for IMC management interfaces and alert on deviations
• Configure centralized logging for all IMC instances and correlate events across the infrastructure
• Implement file integrity monitoring on IMC firmware and configuration files to detect unauthorized modifications
• Regularly audit user accounts and access permissions within the IMC management interface

How to Mitigate CVE-2020-3470

Immediate Actions Required

• Apply the security patches provided by Cisco to all affected IMC firmware versions immediately
• Restrict network access to IMC management interfaces using firewall rules and network segmentation
• Ensure IMC management interfaces are not exposed to untrusted networks or the internet
• Review IMC access logs for any suspicious activity that may indicate prior exploitation attempts
• Implement multi-factor authentication for administrative access to management interfaces where supported

Patch Information

Cisco has released security updates to address these vulnerabilities. Administrators should consult the Cisco Security Advisory for specific fixed firmware versions applicable to their hardware platforms.

The advisory provides detailed version information for:

• Cisco UCS C-Series M3, M4, and M5 rack servers
• Cisco UCS E-Series servers
• Cisco UCS S-Series storage servers
• Cisco Enterprise NFV Infrastructure Software

Workarounds

• Implement strict network segmentation to isolate IMC management interfaces from general network traffic
• Use access control lists (ACLs) to limit IMC API access to known administrative IP addresses only
• Consider disabling unused API features if supported by your firmware version
• Deploy a jump host or bastion server for all IMC administrative access to provide an additional security layer

# Example: Network ACL to restrict IMC API access (platform-specific syntax may vary)
# Permit only trusted management subnet to access IMC
access-list IMC_MGMT_ACL permit tcp 10.10.10.0/24 any eq 443
access-list IMC_MGMT_ACL permit tcp 10.10.10.0/24 any eq 80
access-list IMC_MGMT_ACL deny tcp any any eq 443
access-list IMC_MGMT_ACL deny tcp any any eq 80

# Apply to management interface (adjust interface as needed)
interface management0
  ip access-group IMC_MGMT_ACL in