CVE-2019-12664 : Exploit Details and Defense Strategies

A weakness has been identified in the Dialer interface feature for ISDN connections in Cisco IOS XE Software for Cisco 4000 Series Integrated Services Routers (ISRs). This vulnerability can potentially be exploited by an unauthorized attacker in close proximity to pass IPv4 traffic through an ISDN channel before the successful completion of PPP authentication.

Understanding CVE-2019-12664

This CVE involves a vulnerability in Cisco IOS XE Software that allows unauthorized passage of IPv4 traffic through an unauthenticated ISDN connection.

What is CVE-2019-12664?

The vulnerability arises from inadequate verification of the state of the PPP IP Control Protocol (IPCP). Exploiting this vulnerability involves an attacker initiating an ISDN call to a vulnerable device and sending traffic through the ISDN channel prior to successful PPP authentication.

The Impact of CVE-2019-12664

CVSS Base Score: 4.7 (Medium Severity)
Attack Vector: Adjacent Network
Attack Complexity: Low
Integrity Impact: Low
Privileges Required: None
Scope: Changed
Vector String: CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Technical Details of CVE-2019-12664

This section provides detailed technical information about the vulnerability.

Vulnerability Description

The vulnerability allows an attacker to pass IPv4 traffic through an unauthenticated ISDN connection before successful PPP authentication due to insufficient validation of the PPP IP Control Protocol (IPCP) state.

Affected Systems and Versions

Product: Cisco IOS XE Software
Vendor: Cisco
Affected Version: Unspecified

Exploitation Mechanism

Attacker initiates an ISDN call to a vulnerable device and sends traffic through the ISDN channel before successful PPP authentication.
Unauthenticated remote attacker routes traffic through a vulnerable device with misconfigured CHAP passwords.

Mitigation and Prevention

Protect your systems from this vulnerability by following these steps:

Immediate Steps to Take

Ensure proper authentication mechanisms are in place for ISDN connections.
Regularly monitor network traffic for any suspicious activities.

Long-Term Security Practices

Implement network segmentation to limit the impact of potential breaches.
Keep systems up to date with the latest security patches.

Patching and Updates

Apply relevant security patches provided by Cisco to address this vulnerability.