Cisco 7xx routers running IOS 700 may crash using a password buffer overflow
| cisco-7xxcrash (699) |  Medium Risk |
Description:
Cisco 7xx routers running IOS 700 are vulnerable to a denial of service attack caused by a buffer overflow. By establishing a Telnet connection to the router and entering a very long password string, a remote attacker can overflow a buffer and cause the router to crash, denying service to legitimate users.
Platforms Affected:
- Cisco, IOS 4.1
- Cisco, IOS 4.1.1
- Cisco, IOS 4.1.2
Remedy:
A fix was integrated in IOS/700 version 4.1(2.1). The first regular production release containing this fix was 4.2(1). Cisco will be making the fixed software available to all IOS/700 customers who are presently running 4.1 software, regardless of contract status.
Workaround: The vulnerability may be avoided by controlling access to the system console port, and by restricting access to the telnet service to trusted hosts. Telnet access may be restricted either by using filters on firewalls or surrounding routers, or by using filters on the 7xx router itself.
To restrict access to the telnet service on a 7xx router running 4.1(x) software to a single trusted management host, use the command "set ip filter tcp in source = not trusted-ip-address destination = 7xx-address:23 block". The command should be applied in every profile that may be active when the router is connected to a potentially hostile network.
Consequences:
Denial of Service
References:
- CIAC Information Bulletin I-020, Cisco 7xx Password Buffer Overflow at http://ciac.llnl.gov/ciac/bulletins/i-020.shtml.
- Cisco Systems Field Notice, December 15, 1997, 7xx Router Password Buffer Overflow at http://www.cisco.com/warp/public/770/pwbuf-pub.shtml.
- BID-704: Cisco IOS/700 Router Password Buffer Overflow
- CVE-1999-0230: Buffer overflow in Cisco 7xx routers through the telnet service.
- OSVDB ID: 1102: Cisco 700 Router Telnet Password Overflow DoS
Reported:
Dec 15, 1997
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