CVE-2026-20093: Cisco IMC Auth Bypass Vulnerability

CVE-2026-20093 Overview

A critical authentication bypass vulnerability has been identified in the change password functionality of Cisco Integrated Management Controller (IMC). This vulnerability allows an unauthenticated, remote attacker to bypass authentication mechanisms and gain administrative access to the system.

The flaw stems from incorrect handling of password change requests, enabling attackers to send specially crafted HTTP requests to affected devices. Successful exploitation could allow an attacker to modify the passwords of any user on the system, including administrative accounts, effectively granting full system access.

Critical Impact

Unauthenticated remote attackers can bypass authentication and gain Admin-level access to Cisco IMC systems by exploiting improper password change request handling.

Affected Products

• Cisco Integrated Management Controller (IMC)
• Cisco IMC-based server management interfaces
• Systems utilizing Cisco IMC for remote management

Discovery Timeline

• April 1, 2026 - CVE-2026-20093 published to NVD
• April 1, 2026 - Last updated in NVD database

Technical Details for CVE-2026-20093

Vulnerability Analysis

This authentication bypass vulnerability (CWE-20: Improper Input Validation) affects the password change functionality within Cisco Integrated Management Controller. The vulnerability allows unauthenticated attackers to circumvent authentication controls entirely, gaining the ability to alter credentials for any user account on the system.

The network-accessible nature of this vulnerability means that any Cisco IMC instance exposed to the network could be targeted without requiring any prior authentication or user interaction. Once exploited, an attacker gains the capability to change administrative passwords and assume full control of the management interface.

Root Cause

The root cause of this vulnerability is improper input validation in the password change request handling mechanism. The Cisco IMC fails to properly verify that password change requests originate from authenticated and authorized users before processing them. This allows unauthenticated requests to be processed as if they came from legitimate users with appropriate privileges.

Attack Vector

The attack is conducted over the network by sending a crafted HTTP request to the vulnerable Cisco IMC endpoint. The attacker does not require any privileges or user interaction to exploit this vulnerability. The attack sequence involves:

1. Identifying a network-accessible Cisco IMC instance
2. Crafting a malicious HTTP request targeting the password change functionality
3. Sending the request to bypass authentication checks
4. Modifying the password of an administrative user
5. Authenticating to the system using the newly set credentials

The vulnerability can be exploited remotely without authentication. Attackers target the password change endpoint with specially crafted HTTP requests that exploit the improper validation logic. For detailed technical information, refer to the Cisco Security Advisory.

Detection Methods for CVE-2026-20093

Indicators of Compromise

• Unexpected password change events for administrative accounts in Cisco IMC logs
• Unauthorized HTTP requests to the password change endpoint from external IP addresses
• Login activity from unknown or suspicious IP addresses following password modifications
• Multiple failed authentication attempts followed by successful password changes

Detection Strategies

• Monitor HTTP traffic to Cisco IMC interfaces for anomalous password change requests
• Implement network-based intrusion detection rules to identify exploitation attempts
• Review Cisco IMC audit logs for unauthorized credential modifications
• Deploy web application firewalls (WAF) to inspect and filter malicious requests

Monitoring Recommendations

• Enable verbose logging on all Cisco IMC instances
• Configure alerting for any password change events, particularly for administrative accounts
• Implement network segmentation to restrict access to management interfaces
• Establish baseline behavior for Cisco IMC access patterns to identify anomalies

How to Mitigate CVE-2026-20093

Immediate Actions Required

• Restrict network access to Cisco IMC interfaces using firewall rules and access control lists
• Isolate Cisco IMC management interfaces on dedicated management VLANs
• Audit current administrative accounts and verify password integrity
• Monitor for any indicators of compromise or unauthorized access attempts

Patch Information

Cisco has released a security advisory addressing this vulnerability. Organizations should review the Cisco Security Advisory for specific patch information and upgrade guidance. Apply the latest firmware updates to all affected Cisco IMC instances as soon as they become available.

Workarounds

• Implement strict network access controls limiting Cisco IMC access to trusted management networks only
• Use VPN or jump hosts for remote management access instead of exposing IMC interfaces directly
• Enable multi-factor authentication where supported for additional security layers
• Consider temporarily disabling external network access to IMC until patches are applied

# Example: Restrict access to Cisco IMC management interface using firewall rules
# Replace MANAGEMENT_NETWORK with your trusted management subnet

# iptables example - allow only management network
iptables -A INPUT -p tcp --dport 443 -s MANAGEMENT_NETWORK -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP

# Verify Cisco IMC is not exposed to untrusted networks
nmap -p 443 <IMC_IP_ADDRESS> --script http-title