Skip to main content

Cisco Releases Security Update for Actively Exploited Vulnerability CVE-2023-20269

The exploited zero-day vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could lead to unauthorised access

Threat ID:
CC-4375
Threat Severity:
Medium
Published:
11 September 2023 12:46 PM
Report a cyber attack: call 0300 303 5222 or email [email protected]

Summary

The exploited zero-day vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could lead to unauthorised access

Affected platforms

The following platforms are known to be affected:

Cisco Adaptive Security Appliance (ASA) Software

Cisco FirePower Threat Defense (FTD)

Threat details

Introduction

Cisco has released a security update for an exploited zero-day vulnerability in the remote access VPN feature of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software. The vulnerability CVE-2023-20269 is due to improper separation of authentication, authorisation, and accounting (AAA) between the remote access VPN feature and the HTTPS management and site-to-site VPN features.

An unauthenticated, remote attacker could exploit this vulnerability by specifying a default connection profile/tunnel group while conducting a brute-force attack or while establishing a clientless SSL VPN session using valid credentials. A successful exploit could allow the attacker to achieve one or both of the following:

  • Identify valid credentials that could then be used to establish an unauthorised remote access VPN session.
  • Establish a clientless SSL VPN session (only when running Cisco ASA Software Release 9.16 or earlier).

Remediation advice

Affected organisations are encouraged to review the Cisco Security Advisory cisco-sa-asaftd-ravpn-auth-8LyfCkeC for more information.

Cisco's recommendations in regard to this vulnerability are as follows:

Secure Default Remote Access VPN Profiles

When the default remote access VPN connection profiles/tunnel groups DefaultRAGroup and DefaultWEBVPNGroup are not used, Cisco recommends preventing authentication attempts and remote access VPN session establishment using these default connection profiles/tunnel groups by pointing them to a sinkhole AAA server. To do this, use the following steps:

  1. Configure a dummy Lightweight Directory Access Protocol (LDAP) server, as shown in the following example:

    aaa-server AAA_Sinkhole protocol ldap

    Do not add any additional configuration for this AAA server.
     
  2. Point DefaultRAGroup, DefaultWEBVPNGroup, or both to this dummy LDAP server, as shown for the DefaultWEBVPNGroup in the following example:

    tunnel-group DefaultWEBVPNGroup general-attributes authentication-server-group AAA_Sinkhole

Enable Logging

Cisco recommends enabling logging to a remote syslog server for improved correlation and auditing of network and security incidents across various network devices. For information on how to configure logging, see Cisco's platform-specific guides.

CVE Vulnerabilities

Status Published

CVE-2023-20269

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. This vulnerability is due to improper separation of authentication, authorization, and accounting (AAA) between the remote access VPN feature and the HTTPS management and site-to-site VPN features. An attacker could exploit this vulnerability by specifying a default connection profile/tunnel group while conducting a brute force attack or while establishing a clientless SSL VPN session using valid credentials. A successful exploit could allow the attacker to achieve one or both of the following: Identify valid credentials that could then be used to establish an unauthorized remote access VPN session. Establish a clientless SSL VPN session (only when running Cisco ASA Software Release 9.16 or earlier). Notes: Establishing a client-based remote access VPN tunnel is not possible as these default connection profiles/tunnel groups do not and cannot have an IP address pool configured. This vulnerability does not allow an attacker to bypass authentication. To successfully establish a remote access VPN session, valid credentials are required, including a valid second factor if multi-factor authentication (MFA) is configured. Cisco will release software updates that address this vulnerability. There are workarounds that address this vulnerability.

Last edited: 11 September 2023 2:27 pm