Rule:  

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Sid:
1866

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Summary:
This event is generated when an attempt is made to overflow a buffer by supplying a very long username to a POP3 service.

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Impact:
Serious. Several POP3 servers are vulnerable to USER buffer overflows.

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Detailed Information:
A very long string data in place of the username can lead to a buffer overflow situation.

A buffer overflow attack can be used to execute arbitrary code (remote shell). A Denial of Service (DoS) is also possible.
 
Check your POP3 service for this vulnerability with common vulnerability scanners.

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Affected Systems:
Ipswich IMail 5.0.5, 5.0.6 and 5.0.7 for Windows NT.
Other POP3 mail systems may be affected.

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Attack Scenarios:
A attacker may first check the POP3 daemon version and try a buffer overflow attack using a long username string supplied with the USER command.

This may result in full compromise of the host. A Remote shell can be bound to a port after the attack. 

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Ease of Attack:
Simple. Exploit scripts are available.

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False Positives:
None known.

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False Negatives:
None known

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Corrective Action:
Apply the appropriate vendor supplied patches.

Upgrade to the latest non-affected version of the software.

Check for other events generated by the source IP address.

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Contributors:
Snort documentation contributed by Ueli Kistler, <u.kistler@engagesecurity.com>
Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References:


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