Rule:

--
Sid:
2034

--
Summary:
A request has been made to rpc.ypserv from an external source that 
should not have access to this service. This may be indicative of an 
intelligence gathering activity as a prelude to a more serious 
compromise of system resources.

service against the target host.

--
Impact:
Disclosure of sensitive system information to an unauthorized user. 
Possible denial of service.

--
Detailed Information:
The rpc.ypserv daemon queries information in the local NIS maps. A 
response to this query may divulge important information to the user 
performing the query. This could lead to futher exploitation of 
resources on the network.

In addition, a vulnerability exists in ypserv on some Linux platforms 
that could lead to a buffer overflow and root compromise of the target 
host. This is achieved by making a multitude of requests for a NIS map 
that does not exist.

--
Affected Systems:
Multiple systems running versions of ypserv prior to 2.5.

--
Attack Scenarios:
The attacker can craft a malicious request to rpc.ypserv such that 
valuable information can be returned to the attacker.

In the case of a buffer overflow, the attacker might issue a large 
therefore, be seen many times.

--
Ease of Attack:
Simple

--
False Positives:
None Known

--
False Negatives:
None Known

--
Corrective Action:
Disallow all RPC requests from external sources and use a firewall to 
block access to RPC ports from outside the LAN.

Upgrade ypserv to the latest version.

Use /var/yp/securenets to list the hosts allowed to access this resource
where appropriate.

--
Contributors:
Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

--
Additional References:

Bugtraq:
http://www.securityfocus.com/bid/6016
http://www.securityfocus.com/bid/5914

CVE:
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2002-1232
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-1043
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2000-1042

--
