Vulnerabilities > CVE-2017-6664 - Improper Certificate Validation vulnerability in Cisco IOS XE
Summary
A vulnerability in the Autonomic Networking feature of Cisco IOS XE Software could allow an unauthenticated, remote, autonomic node to access the Autonomic Networking infrastructure of an affected system, after the certificate for the autonomic node has been revoked. This vulnerability affected devices that are running Release 16.x of Cisco IOS XE Software and are configured to use Autonomic Networking. This vulnerability does not affect devices that are running an earlier release of Cisco IOS XE Software or devices that are not configured to use Autonomic Networking. More Information: CSCvd22328. Known Affected Releases: 15.5(1)S3.1 Denali-16.2.1.
Vulnerable Configurations
Common Weakness Enumeration (CWE)
Common Attack Pattern Enumeration and Classification (CAPEC)
- Creating a Rogue Certificate Authority Certificate An attacker exploits a weakness in the MD5 hash algorithm (weak collision resistance) to generate a certificate signing request (CSR) that contains collision blocks in the "to be signed" part. The attacker specially crafts two different, but valid X.509 certificates that when hashed with the MD5 algorithm would yield the same value. The attacker then sends the CSR for one of the certificates to the Certification Authority which uses the MD5 hashing algorithm. That request is completely valid and the Certificate Authority issues an X.509 certificate to the attacker which is signed with its private key. An attacker then takes that signed blob and inserts it into another X.509 certificate that the attacker generated. Due to the MD5 collision, both certificates, though different, hash to the same value and so the signed blob works just as well in the second certificate. The net effect is that the attackers' second X.509 certificate, which the Certification Authority has never seen, is now signed and validated by that Certification Authority. To make the attack more interesting, the second certificate could be not just a regular certificate, but rather itself a signing certificate. Thus the attacker is able to start their own Certification Authority that is anchored in its root of trust in the legitimate Certification Authority that has signed the attackers' first X.509 certificate. If the original Certificate Authority was accepted by default by browsers, so will now the Certificate Authority set up by the attacker and of course any certificates that it signs. So the attacker is now able to generate any SSL certificates to impersonate any web server, and the user's browser will not issue any warning to the victim. This can be used to compromise HTTPS communications and other types of systems where PKI and X.509 certificates may be used (e.g., VPN, IPSec) .
Nessus
NASL family | CISCO |
NASL id | CISCO-SA-20170726-ANICRL.NASL |
description | According to its self-reported version, Cisco IOS XE Software is affected by a vulnerability in the Autonomic Networking feature because the affected software does not transfer certificate revocation lists (CRLs) across Autonomic Control Plane (ACP) channels. An unauthenticated, remote attacker can exploit this, by connecting an autonomic node that has a known and revoked certificate to the autonomic domain of an affected system. The attacker can then insert a previously trusted autonomic node into the autonomic domain of an affected system after the certificate for the node has been revoked. Please see the included Cisco BIDs and Cisco Security Advisory for more information. Note that Nessus has not tested for this issue but has instead relied only on the application |
last seen | 2020-06-01 |
modified | 2020-06-02 |
plugin id | 131131 |
published | 2019-11-20 |
reporter | This script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof. |
source | https://www.tenable.com/plugins/nessus/131131 |
title | Cisco IOS XE Software Autonomic Networking Infrastructure Certificate Revocation (cisco-sa-20170726-anicrl) |
References
- http://www.securityfocus.com/bid/99986
- http://www.securityfocus.com/bid/99986
- http://www.securitytracker.com/id/1038997
- http://www.securitytracker.com/id/1038997
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170726-anicrl
- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170726-anicrl