Rule:

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Sid:

1549

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Summary:
This event is generated when an attempt is made to overflow a buffer in an SMTP server via a long SMTP HELO command. 

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Impact:
A remote attacker could exploit this vulnerability to cause a denial of service, or possibly execute arbitrary code.

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Detailed Information:
Most SMTP servers do not properly validate the input string. A buffer overflow may occur when an attacker use a HELO command followed by 1024+ characters. If the server is vulnerable ,it will crash or close the connection, otherwise it will give an error message.

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Affected Systems:

	SMTP servers Any version
	AppleShare IP Mail Server Any version
	Mercury Mail Server Any version
	SLMail v2.6 and earlier
	

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Attack Scenarios:
telnet victim.foo.com 25
helo victim
220 victim SMTP Server Ready 
HELO XXXXXXXXXXX[a thousand of these]XXXXXXXX 

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

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Contributors:

Sourcefire Research Team
Brian Caswell <bmc@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>
Snort documentation contributed by Nawapong Nakjang (tony@ksc.net, tonie@thai.com)

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Additional References:

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