Open Software Solutions

Windows Vista Service Pack 1 and Windows Server 2008 now include support for Structured Exception Handling Overwrite Protection (SEHOP). This feature is designed to block exploits that use the Structured Exception Handler (SEH) overwrite technique. This protection mechanism is provided at run-time. Therefore, it helps protect applications regardless of whether or not they have been compiled with the latest improvements, such as /SAFESEH. We recommend that Windows Vista users enable this feature to help increase the security profile of their systems.

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Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

By default, SEHOP is enabled in Windows Server 2008. By default, it is disabled in Windows Vista. To enable SEHOP manually, follow these steps:

1.	Click Start, click Run, type regedit, and then press ENTER.
2.	Locate the following registry subkey: HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Control Session Manager kernel DisableExceptionChainValidation Note If you cannot find the DisableExceptionChainValidation registry entry under the HKEY_LOCAL_MACHINE SYSTEM CurrentControlSet Control Session Manager kernel subkey, follow these steps to create it: a. Right-click kernel, point to New, and then click DWORD Value. b. Type DisableExceptionChainValidation, and then press ENTER.
3.	Double-click DisableExceptionChainValidation.
4.	Change the value of the DisableExceptionChainValidation registry entry to 0 to enable it, and then click OK. Note A value of 1 disables the registry entry. A value of 0 enables it.
5.	Exit Registry Editor.

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Known Issues

If you enable SEHOP, existing versions of Cygwin, Skype, and Armadillo-protected applications may not work correctly.

Note To resolve this issue, contact the software vendor for an update.

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Preventing the Exploitation of SEH Overwrites

For more information about a technique that you can use to help prevent the exploitation of SEH overwrites, visit the following third-party Web site:

The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products. Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

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