ZDI-07-073: Microsoft Internet Explorer setExpression Vulnerability Dec 11 2007 09:54PM
zdi-disclosures 3com com
ZDI-07-073: Microsoft Internet Explorer setExpression Code Execution



December 11, 2007

-- CVE ID:


-- Affected Vendor:


-- Affected Products:

Internet Explorer 5.01 SP4

Internet Explorer 6

Internet Explorer 7

-- TippingPoint(TM) IPS Customer Protection:

TippingPoint IPS customers have been protected against this

vulnerability by Digital Vaccine protection filter ID .

For further product information on the TippingPoint IPS:


-- Vulnerability Details:

This vulnerability allows remote attackers to execute arbitrary code on

vulnerable installations of Microsoft Internet Explorer. User

interaction is required to exploit this vulnerability in that the

target must visit a malicious page.

The specific flaw exists in the CRecalcProperty function in mshtml.dll.

When rendering HTML after calling the setExpression methods, followed by

a modification of the outerHTML property of a programatically created

element. The vulnerable code dereferences a previously freed memory

location which can be leveraged to execute arbitrary code.

-- Vendor Response:

Microsoft has issued an update to correct this vulnerability. More

details can be found at:


-- Disclosure Timeline:

2007.07.20 - Vulnerability reported to vendor

2007.12.11 - Coordinated public release of advisory

-- Credit:

This vulnerability was discovered by an anonymous researcher.

-- About the Zero Day Initiative (ZDI):

Established by TippingPoint, The Zero Day Initiative (ZDI) represents

a best-of-breed model for rewarding security researchers for responsibly

disclosing discovered vulnerabilities.

Researchers interested in getting paid for their security research

through the ZDI can find more information and sign-up at:


The ZDI is unique in how the acquired vulnerability information is used.

3Com does not re-sell the vulnerability details or any exploit code.

Instead, upon notifying the affected product vendor, 3Com provides its

customers with zero day protection through its intrusion prevention

technology. Explicit details regarding the specifics of the

vulnerability are not exposed to any parties until an official vendor

patch is publicly available. Furthermore, with the altruistic aim of

helping to secure a broader user base, 3Com provides this vulnerability

information confidentially to security vendors (including competitors)

who have a vulnerability protection or mitigation product.

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