CVE-2025-20285: Cisco ISE Auth Bypass Vulnerability

CVE-2025-20285 Overview

A vulnerability exists in the IP Access Restriction feature of Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC) that could allow an authenticated, remote attacker to bypass configured IP access restrictions. This authorization bypass flaw enables attackers with valid administrative credentials to log in to the device's API from IP addresses that should be blocked by the access control configuration.

The vulnerability stems from improper enforcement of access controls configured through the IP Access Restriction feature. While the security control is designed to limit administrative access to specific trusted IP addresses, the flawed implementation allows authentication requests via the API to circumvent these restrictions entirely.

Critical Impact

Authenticated attackers can bypass IP-based access controls to gain administrative access from unauthorized network locations, potentially compromising network security policies and enabling lateral movement from untrusted network segments.

Affected Products

• Cisco Identity Services Engine (ISE) versions 3.3.0 through 3.3.0 Patch 6
• Cisco Identity Services Engine (ISE) versions 3.4.0 through 3.4.0 Patch 1
• Cisco Identity Services Engine Passive Identity Connector (ISE-PIC) versions 3.3.0 through 3.4.0 Patch 1

Discovery Timeline

• July 16, 2025 - CVE-2025-20285 published to NVD
• July 22, 2025 - Last updated in NVD database

Technical Details for CVE-2025-20285

Vulnerability Analysis

This vulnerability is classified under CWE-302 (Authentication Bypass by Assumed-Immutable Data), indicating that the access control mechanism relies on data that attackers can manipulate or circumvent. In this case, the IP Access Restriction feature fails to properly validate and enforce source IP restrictions when authentication requests are submitted through the API interface.

The core issue is that while the web-based management interface may correctly enforce IP restrictions, the API endpoints do not consistently apply the same access control checks. This creates an inconsistent security posture where administrators believe they have restricted access to specific IP ranges, but the API remains accessible from any network location.

The vulnerability requires the attacker to possess valid administrative credentials, which somewhat limits the attack surface. However, in scenarios involving credential theft, insider threats, or compromised administrator accounts, this bypass allows attackers to access the ISE infrastructure from network segments that should be untrusted or segmented.

Root Cause

The root cause of CVE-2025-20285 is improper enforcement of IP-based access controls within the Cisco ISE API authentication pathway. The IP Access Restriction feature is designed to limit which source IP addresses can authenticate to the administrative interfaces, but this enforcement is not consistently applied across all entry points.

The API authentication mechanism processes credentials without adequately verifying that the source IP address is within the allowed range configured by administrators. This represents a gap between the security policy configuration and its actual enforcement at the application layer.

Attack Vector

The attack vector for this vulnerability is network-based and requires the following conditions:

1. Valid Credentials: The attacker must possess valid administrative credentials for the Cisco ISE deployment
2. Network Connectivity: The attacker must be able to reach the Cisco ISE API endpoint over the network
3. IP Restriction Configured: The target ISE deployment must have IP Access Restriction enabled with a configuration that should block the attacker's source IP

An attacker who has obtained administrative credentials through phishing, credential stuffing, or other means can leverage this vulnerability to access the ISE administrative functions from any network location. This defeats the defense-in-depth strategy that IP restrictions are designed to provide.

The attack scenario typically involves an attacker authenticating directly to the ISE API from an unauthorized IP address, bypassing restrictions that would have blocked the same credentials if used through the standard web interface.

Detection Methods for CVE-2025-20285

Indicators of Compromise

• Successful API authentication events from IP addresses outside the configured IP Access Restriction allowlist
• Administrative login patterns showing access from unexpected geographic locations or network segments
• API access logs indicating authentication from IP ranges that should be blocked by policy
• Discrepancies between web interface access logs and API access logs for the same administrator accounts

Detection Strategies

• Correlate API authentication logs with the configured IP Access Restriction rules to identify policy violations
• Implement external monitoring of authentication events that cross-references source IPs against allowed ranges
• Configure SIEM rules to alert on administrative API access from IP addresses not matching the ISE IP restriction configuration
• Audit API access patterns for administrator accounts, focusing on source IP diversity

Monitoring Recommendations

• Enable comprehensive logging for all API authentication attempts, including source IP addresses
• Deploy network monitoring to track connections to ISE API endpoints from unexpected network segments
• Implement regular audits comparing actual API access patterns against intended IP restriction policies
• Consider implementing additional network-layer access controls (firewall rules) as a compensating control until patches are applied

How to Mitigate CVE-2025-20285

Immediate Actions Required

• Review current IP Access Restriction configurations and verify all intended restrictions are in place
• Implement network-level firewall rules to restrict access to ISE API endpoints as a compensating control
• Audit recent API authentication logs for any suspicious access from unauthorized IP addresses
• Consider temporarily disabling API access from untrusted networks until patches can be applied
• Ensure all administrative credentials are strong and have not been compromised

Patch Information

Cisco has released security updates to address this vulnerability. Administrators should consult the Cisco Security Advisory for specific patch versions and upgrade guidance.

Organizations running affected versions of Cisco ISE or ISE-PIC should prioritize upgrading to fixed releases as specified in the vendor advisory. The following versions are confirmed vulnerable:

• Cisco ISE 3.3.0 through 3.3.0 Patch 6
• Cisco ISE 3.4.0 through 3.4.0 Patch 1
• Cisco ISE-PIC corresponding versions

Workarounds

• Implement firewall rules at the network perimeter to restrict access to ISE management interfaces and API endpoints
• Use VPN requirements for all administrative access to ensure connections originate from trusted network segments
• Deploy additional authentication factors (MFA) for administrative accounts to limit the impact of credential compromise
• Segment ISE management interfaces on a dedicated management VLAN with strict access controls

# Example firewall rule to restrict ISE API access (adjust for your environment)
# Restrict access to ISE admin port to specific management subnet
iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP