Rule:

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Sid:
2034

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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.

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

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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.

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

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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.

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Ease of Attack:
Simple

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False Positives:
None Known

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False Negatives:
None Known

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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.

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

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Additional References:

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

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