Cisco CHAP authentication failure allows unauthorized PPP connections
| cisco-CHAP (570) |  High Risk |
Description:
The system is vulnerable to a failure of CHAP authentication through the use of PPP connections. Cisco IOS, as well as IOS/700 software, allows dial-up users to obtain a PPP connection without a password. An attacker possessing source code and information about the network (such as usernames and IP addresses) can modify their own CHAP implementation to exploit this vulnerability.
Systems using PAP for PPP authentication are not vulnerable. Systems not configured for PPP are not vulnerable. If the keywords ppp and chap do not both appear in your system configuration file, you are not vulnerable.
Platforms Affected:
- Cisco, IOS 10.3
- Cisco, IOS 11.0
- Cisco, IOS 11.1
- Cisco, IOS 11.2
- Cisco, IOS 11.2P
- Cisco, IOS 4.1
- Cisco, IOS 9.1
Remedy:
IOS users should upgrade to 10.3(19a), 11.0(17), 11.1(14), 11.2(4)F1, 11.2(8), or the latest supported version for the device. As with any software upgrade, you should verify that your hardware can support the new software before upgrading.
As a workaround, affected users who want to protect their systems must upgrade their software or stop using CHAP authentication. Alternatives to CHAP authentication include PAP authentication and reliance on Caller ID information.
Patches: Cisco customers with contracts should obtain upgraded software through their regular update channels (via Cisco's Web site). Customers without contracts should contact Cisco TAC at tac@cisco.com.
Consequences:
Gain Access
References:
- CIAC Information Bulletin I-002a, Cisco CHAP Authentication Vulnerability at http://www.ciac.org/ciac/bulletins/i-002a.shtml.
- Cisco Systems Field Notice, October 1, 1997, Vulnerabilities in Cisco CHAP Authentication at http://www.cisco.com/warp/public/770/chapvuln-pub.shtml.
- BID-693: Cisco IOS CHAP Authentication Vulnerabilities
- CVE-1999-0160: Some classic Cisco IOS devices have a vulnerability in the PPP CHAP authentication to establish unauthorized PPP connections.
- OSVDB ID: 1099: Cisco IOS CHAP Authentication Bypass
Reported:
Oct 01, 1997
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