14th Apr 2003 [SBWID-6143]
COMMAND
Linsys BEFVP41 VPN router information leakage
SYSTEMS AFFECTED
versions 1.40.3f and 1.40.4 tested positively
PROBLEM
Branson Matheson [branson(at)windborne(dot)net] reported:
While the following is not a critical vulnerability, it is a serious
problem for those that are implementing these VPN routers in production
environments.
The MIB information available from the default 'public' community name
on the external interface of a Linksys VPN router includes information
about the hosts on the inside of the protected network including
routes, hardware addresses ( MAC ), and some configuration information.
What is NOT available include information about the VPN's configured,
any preshared keys, VPN routes, or endpoint IP's.
Testability
===========
install the net-snmp package and run the following on any Linksys
router that has not had it's community names altered:
snmpwalk -v 1 -c public {ip}
Mitigating factor
=================
Stefan Laudat [stefan(at)worldbank(dot)ro] reported that he never found
SNMP running on the external interface, even using the router directly
out of the box:
I'd kiss a frog if this was true. Actually I use over 50 of these toys
in production and it would have made me very happy if I could use SNMP
from outside the external interface. No surprise for me that the tech
support did not respond on your emails, it's likely that they're using
outsourced software in their products, since I've had a nice discussion
some time ago with one of their support representative who didn't ever
know what I was talking about when referring words like 'Crypto engine
failure','isakmp' etc I also have some bug issues open in their tech
support, which remained unanswered until today. What I know is they
told me SNMP is *not* usable from outside, and I've tested this for
myself. All filters were off, not blocking any wan request, remote
management on. Recently I've bought a new one which contains version
1.40.5, still unreleased on the web site, so hang on for this release.
Once again, don't rely on their support (which is stinky), maybe Cisco
will fix this as they've bought them some weeks ago.
SOLUTION
Change the community names configured in the 'password' section of the
VPN routers web based config tool. There is no current way to disable
SNMP.