CVE-2023-20254: Cisco SD-WAN Manager Auth Bypass Flaw

CVE-2023-20254 Overview

A vulnerability in the session management system of the Cisco Catalyst SD-WAN Manager multi-tenant feature could allow an authenticated, remote attacker to access another tenant that is being managed by the same Cisco Catalyst SD-WAN Manager instance. This vulnerability requires the multi-tenant feature to be enabled.

This vulnerability is due to insufficient user session management within the Cisco Catalyst SD-WAN Manager system. An attacker could exploit this vulnerability by sending a crafted request to an affected system. A successful exploit could allow the attacker to gain unauthorized access to information about another tenant, make configuration changes, or possibly take a tenant offline causing a denial of service condition.

Critical Impact

Authenticated attackers can cross tenant boundaries to access sensitive data, modify configurations, or cause denial of service to other tenants in a multi-tenant SD-WAN environment.

Affected Products

• Cisco SD-WAN Manager (multi-tenant deployments)
• Cisco Catalyst SD-WAN Manager with multi-tenant feature enabled
• Multiple versions of Cisco SD-WAN Manager software

Discovery Timeline

• 2023-09-27 - CVE-2023-20254 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-20254

Vulnerability Analysis

This vulnerability represents a Broken Access Control issue stemming from improper session management in multi-tenant environments. The Cisco Catalyst SD-WAN Manager allows multiple tenants to be managed from a single instance, requiring robust session isolation to prevent cross-tenant access. Due to insufficient user session management, authenticated users can craft requests that bypass tenant isolation mechanisms, enabling unauthorized access to other tenants' resources.

The vulnerability is classified under CWE-732 (Incorrect Permission Assignment for Critical Resource), indicating that the session management system fails to properly enforce permission boundaries between tenants. This allows an attacker with valid credentials for one tenant to access, modify, or disrupt another tenant's SD-WAN environment.

Root Cause

The root cause lies in the insufficient user session management within the Cisco Catalyst SD-WAN Manager system. The session handling mechanism does not adequately validate and enforce tenant-specific boundaries, allowing authenticated users to escape their designated tenant context through crafted requests. This improper permission assignment for critical resources enables cross-tenant access that should be strictly prohibited in multi-tenant architectures.

Attack Vector

The attack requires network access and valid authentication credentials (low privileges). An authenticated attacker exploits this vulnerability by sending crafted requests to the affected system that manipulate session parameters or tenant identifiers. Since no user interaction is required and the attack complexity is low, exploitation is straightforward once the attacker has authenticated access.

The attack flow typically involves:

1. Attacker authenticates to the Cisco Catalyst SD-WAN Manager with valid credentials for their assigned tenant
2. Attacker crafts a request that manipulates session or tenant context parameters
3. The insufficient session validation allows the request to be processed in the context of a different tenant
4. Attacker gains access to the target tenant's data, configuration, or can disrupt their services

Detection Methods for CVE-2023-20254

Indicators of Compromise

• Unusual session activity patterns indicating tenant boundary violations
• Unexpected configuration changes in tenant environments
• Authentication logs showing users accessing resources outside their assigned tenant scope
• API requests with manipulated tenant identifiers or session tokens

Detection Strategies

• Monitor authentication and authorization logs for anomalous cross-tenant access attempts
• Implement session analytics to detect unusual patterns in user session behavior
• Deploy network traffic analysis to identify crafted requests targeting tenant isolation mechanisms
• Review API access logs for requests that reference tenant resources outside the authenticated user's scope

Monitoring Recommendations

• Enable detailed logging on Cisco Catalyst SD-WAN Manager for all session-related events
• Set up alerts for configuration changes across tenant boundaries
• Implement regular audit reviews of multi-tenant access patterns
• Monitor for denial of service indicators affecting specific tenants

How to Mitigate CVE-2023-20254

Immediate Actions Required

• Review the Cisco Security Advisory for affected version details and apply relevant patches
• Audit current multi-tenant configurations for any signs of exploitation
• Restrict network access to the SD-WAN Manager administrative interface to trusted networks only
• Review and validate all user accounts with multi-tenant access

Patch Information

Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for specific version information and upgrade paths. The advisory provides detailed guidance on which software versions contain the fix and the recommended upgrade procedures for affected deployments.

Workarounds

• Disable the multi-tenant feature if not required for operations (note: this changes deployment architecture)
• Implement strict network segmentation to limit access to the SD-WAN Manager interface
• Enforce strong authentication mechanisms including multi-factor authentication for all administrative access
• Apply the principle of least privilege to all user accounts accessing the SD-WAN Manager

# Example: Restrict administrative access via ACL (consult Cisco documentation for your specific version)
# This is a general guidance example - verify against your deployment
access-list SDWAN-MGMT-ACCESS permit tcp trusted-subnet 0.0.0.255 host sdwan-manager-ip eq 443
access-list SDWAN-MGMT-ACCESS deny ip any host sdwan-manager-ip