CVE-2021-36300: Dell EMC iDRAC9 DoS Vulnerability

CVE-2021-36300 Overview

CVE-2021-36300 is an improper input validation vulnerability affecting Dell iDRAC9 firmware versions prior to 5.00.00.00. An unauthenticated remote attacker may potentially exploit this vulnerability by sending a specially crafted malicious request to crash the webserver or cause information disclosure. This firmware vulnerability impacts Dell's integrated Dell Remote Access Controller (iDRAC), a critical out-of-band management interface used to remotely manage and monitor PowerEdge servers.

Critical Impact

Unauthenticated attackers can remotely crash the iDRAC9 webserver or extract sensitive information without any authentication, potentially compromising server management capabilities and exposing confidential configuration data.

Affected Products

• Dell EMC iDRAC9 Firmware versions prior to 5.00.00.00

Discovery Timeline

• 2021-11-23 - CVE CVE-2021-36300 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2021-36300

Vulnerability Analysis

This vulnerability stems from improper input validation in the iDRAC9 web server component. The iDRAC9 interface, which provides out-of-band management capabilities for Dell PowerEdge servers, fails to properly sanitize user-supplied input in certain request handlers. When a malicious request containing specially crafted data is sent to the vulnerable web service, it can trigger two distinct failure modes: either causing the webserver process to crash (denial of service) or leaking sensitive information back to the attacker.

The network-accessible nature of this flaw is particularly concerning since iDRAC interfaces are often exposed on management networks and, in some misconfigurations, may be accessible from the broader network or even the internet. The vulnerability requires no authentication, meaning any attacker with network access to the iDRAC9 interface can attempt exploitation.

Root Cause

The root cause of CVE-2021-36300 is an improper input validation flaw (CWE-89) in the iDRAC9 firmware's web server component. The firmware fails to adequately validate and sanitize input data received through HTTP requests before processing it. This missing validation allows attackers to submit malformed or malicious request parameters that the webserver does not handle safely, resulting in either a crash condition or unintended disclosure of memory contents or system information.

Attack Vector

The attack vector for this vulnerability is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying an exposed iDRAC9 interface on the network
2. Crafting a malicious HTTP request with specially formatted input designed to bypass validation
3. Sending the request to the vulnerable iDRAC9 webserver
4. Achieving either information disclosure (extracting sensitive data) or denial of service (crashing the webserver)

The exploitation does not require valid credentials, making it accessible to any attacker with network connectivity to the iDRAC9 management interface. The attack complexity is low, as exploitation can be achieved through straightforward HTTP requests to the management interface.

Detection Methods for CVE-2021-36300

Indicators of Compromise

• Unexpected iDRAC9 webserver crashes or restarts in system logs
• Unusual or malformed HTTP requests in iDRAC access logs targeting the web management interface
• Anomalous network traffic patterns to iDRAC9 management interfaces, particularly from unauthorized sources
• Evidence of reconnaissance or scanning activity targeting port 443 or 8443 on iDRAC interfaces

Detection Strategies

• Monitor iDRAC9 access logs for malformed or suspicious HTTP requests containing unusual parameters
• Implement network intrusion detection rules to identify potentially malicious traffic patterns targeting iDRAC management interfaces
• Deploy anomaly detection for iDRAC9 webserver process crashes or unexpected service restarts
• Audit network traffic to management interfaces for connections from unauthorized IP addresses

Monitoring Recommendations

• Enable comprehensive logging on all iDRAC9 interfaces and centralize logs for analysis
• Implement alerting for iDRAC9 webserver availability and unexpected restarts
• Monitor management network segments for unauthorized access attempts
• Regularly review iDRAC9 firmware versions across the server fleet to identify unpatched systems

How to Mitigate CVE-2021-36300

Immediate Actions Required

• Update all Dell iDRAC9 firmware to version 5.00.00.00 or later immediately
• Restrict network access to iDRAC9 interfaces to authorized management networks only
• Implement firewall rules to block external access to iDRAC management ports (typically 443 and 8443)
• Audit current iDRAC9 firmware versions across all Dell PowerEdge servers in the environment

Patch Information

Dell has released firmware version 5.00.00.00 to address this vulnerability. Organizations should download and apply this update from the official Dell support channels. Detailed patching instructions and firmware downloads are available in the Dell EMC Support Knowledge Base article. It is strongly recommended to prioritize this update for any iDRAC9 systems that may be accessible from untrusted network segments.

Workarounds

• Isolate iDRAC9 management interfaces on a dedicated, segmented management VLAN with strict access controls
• Implement firewall rules to allow iDRAC9 access only from known, trusted administrator IP addresses
• Consider disabling the iDRAC9 web interface temporarily if remote management is not required until patching is complete
• Deploy a jump host or VPN requirement for all access to iDRAC management networks