Rule:

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Sid:
3461

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Summary:
This event is generated when an attempt is made to overflow a buffer using the Content-Type parameter.

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Impact:
Serious. Code execution is possible.

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Detailed Information:
Internet Explorer does not correctly handle Content-Type or Content-Encoding headers returned from a server. It is possible to overflow a static buffer in urlmon.dll by supplying more than 300 bytes of data in the parameter for those headers.

Specifically the error occurs when an image tag <img> is used to pass the excess data to both those header fields in a server response. Since some email clients use Internet Explorer to process HTML email messages, it is also possible to cause this overflow to occur via email.

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Affected Systems:
Microsoft Windows systems

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Attack Scenarios:
An attacker can supply a malicious HTML file to a mail client containing excess data in the Content-Type and Content-Encoding headers that will overflow the buffer presenting them with the opportunity to write to various parts of memory and possibly execute code of their choosing.

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Ease of Attack:
Simple. Exploit code is publicly available.

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False Positives:
Unsolicited email messages (SPAM) may cause this rule to generate an event.

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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
Alex Kirk <akirk@sourcefire.com>
Nigel Houghton <nigel.houghton@sourcefire.com>

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Additional References

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