CVE-2023-20269: Cisco ASA Auth Bypass Vulnerability

CVE-2023-20269 Overview

A vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct a brute force attack in an attempt to identify valid username and password combinations or an authenticated, remote attacker to establish a clientless SSL VPN session with an unauthorized user.

Critical Impact
The vulnerability could potentially allow attackers to identify valid credentials or establish unauthorized VPN sessions, leading to unauthorized access and potential information exposure.

Affected Products

Cisco Adaptive Security Appliance (ASA) Software
Cisco Firepower Threat Defense (FTD) Software

Discovery Timeline

Published Date: 2023-09-06
Last Modified Date: 2025-10-28

Technical Details for CVE-2023-20269

Vulnerability Analysis

This vulnerability is caused by improper separation of authentication, authorization, and accounting (AAA) between the remote access VPN feature and the HTTPS management and site-to-site VPN features.

Root Cause

The issue arises due to the improper handling of authentication credentials in the specified VPN configurations.

Attack Vector

The attack can be launched remotely over the network, allowing unauthenticated attackers to conduct brute force attacks.

bash

# Example exploitation code (sanitized)
echo "Attempting to brute force VPN credentials..."
for username in {user1,user2,user3}; do
    for password in {pass1,pass2,pass3}; do
        echo "Trying $username:$password"
    done
done

Detection Methods for CVE-2023-20269

Indicators of Compromise

Unusual VPN session logs
Multiple failed login attempts
Unexpected authorized sessions

Detection Strategies

Monitor network traffic for known attack signatures and abnormal VPN access patterns using SentinelOne.

Monitoring Recommendations

Implement continuous log monitoring and anomaly detection to identify brute force attempts. Utilize SentinelOne for automated threat detection.

How to Mitigate CVE-2023-20269

Immediate Actions Required

Disable unnecessary default connection profiles/tunnel groups.
Enforce strong password policies.
Enable multi-factor authentication (MFA).

Patch Information

Cisco plans to release software updates that address this vulnerability. Regularly check Cisco’s advisory for the latest updates.

Workarounds

Administrators can apply access control lists (ACLs) to limit access to VPN services.