PR07-40: Authentication Bypass, Passwords Leakage and SNMP Injection on 3Com AP 8760 Vulnerability Found: 6th November 2007 Vendor Informed: 2nd May 2008 Date Public: 14th November 2008 Severity: Medium Credits: Adrian Pastor of ProCheckUp Ltd (www.procheckup.com). Vulnerability #1: Description: The HTTP authentication mechanism of the 3Com AP 8760 works as follows: 1. Router checks if credentials submitted by user are valid 2. If valid, the router's web interface redirects the user to URLs that should only be available to authenticated admin users What's important to note is that every time an "authenticated" URL is accessed, there is _no_ authentication data being sent within HTTP requests whatsoever. There are no passwords, or session IDs being submitted at all within HTTP requests. Instead, the AP uses the administrator's source IP address as authentication data. This means that the authentication state relies on the false assumption that post-authentication URLs won't be known by an attacker and that the attacker and the administrator will _not_ share the same source IP address. By simply accessing administrative URLs in a browser from _the same IP address_ (i.e.: by sharing the same proxy or NATed IP address), the authentication check can be bypassed completely. Notes: Although URL paths are different, these issues appear to be similar to those found on other 3com router models: http://www.securityfocus.com/bid/11408/discuss http://seclists.org/vulnwatch/2005/q1/0042.html Proof of concept: The following is an example of an administrative page that would allow an attacker to change settings: http://<target_IP>/advanced.htm Vulnerability #2: Description: Additionally, sensitive data such as the admin password is returned within certain pages. Although after bypassing the authentication the attacker wouldn't need to know the admin password anyway, this could be handy for a cracker in scenarios such as the following: 1. The authentication bypass is fixed by updating the firmware to a patched version (attacker would still be able to access the device since he/she knows the admin password) 2. The attacker could try the same password on other servers owned by the same target company since it's a common human weakness to reuse passwords. Proof of concept: The following URLs return the admin password within 'hidden' form fields: http://<target_IP>/s_brief.htm http://<target_IP>/s.htm Vulnerability #3: Description: It's possible to launch SNMP injection attacks. By changing the system name via SNMP, it's possible to inject a persistent XSS payload on several pages including the _login page_. Thus, the attacker has an opportunity to redirect the admin password to his own site by overwriting the login form's action attribute. The payload gets returned within the login page's 'title' tag. i.e.: <title>3Com Wireless 8760 Dual Radio 11a/b/g Access Point PAYLOAD_GOES_HERE</title> Example of snmpset command that changes the AP's system name: snmpset -v2c -c private 192.168.1.1 sysName.0 s "PAYLOAD_GOES_HERE" Successfully tested on: 3COM: AP8760: Dual Radio 11a/b/g Access Point, Software v2.1.13b05_sh, Bootrom v1.2.1, Hardware R02 Note: model and firmware info extracted via SNMP from 'SNMPv2-MIB::sysDescr.0' OID. Consequences: Administrative access can be gained to the device without knowledge of the admin password. The caveat is that the attacker must share the same source IP address with the administrator. Therefore, this vulnerability would mostly be exploited by internal users only. Sensitive information such as administrative credentials can be obtained. Admin passwords can be compromised given that an attacker has first gained SNMP write access. Workaround: No workaround is available for the authentication bypass and passwords leakage issue. SNMP injection can be resolved by disabling SNMP write access. References: http://www.procheckup.com/ http://www.3com.com/products/en_US/detail.jsp?pathtype=purchase&tab=features&sku=3CRWE876075 Legal: Copyright 2008 Procheckup Ltd. All rights reserved. Permission is granted for copying and circulating this Bulletin to the Internet community for the purpose of alerting them to problems, if and only if, the Bulletin is not edited or changed in any way, is attributed to Procheckup, and provided such reproduction and/or distribution is performed for non-commercial purposes. Any other use of this information is prohibited. Procheckup is not liable for any misuse of this information by any third party.