Once that’s done and real address information is gathered, it will try to spawn multiple large objects (hence the use of BigInt) to build a deterministic heap structure. However, this does not guarantee the clearing of data, nor, since the now-deallocated pointer is not actually nullify, that the previously allocated memory cannot be referenced again using the same pointer.Įssentially, the attacker will try to exploit a race condition due to “ missing proper synchronization” between threads using the browser’s built-in BigInt() function and various alloc-then-free routine and trigger UaF condition to leak some real address information to defeat ASLR (Address Space Layout Randomization). When that pointer is deallocated, the memory chunk is updated/merged accordingly to reflect that the block is now free to be allocated again. using malloc()), the memory allocation routine will try to find an empty memory block in the heap (or extend the heap if there isn’t any), generate a memory chunk metadata block that is part of a memory chunk linked list to reflect that the memory location is now allocated/in use, then return the pointer to the newly created memory chunk. Only Windows system components and services have DEP appliedĭEP is enabled for all processes.When a memory block is dynamically allocated (e.g. DataExecutionPrevention_SupportPolicy property value This value corresponds to one of the DEP support policies that are described in the following table. To determine the current DEP support policy, follow these steps.Īt the command prompt, type the following command, and then press ENTER: wmic OS Get DataExecutionPrevention_SupportPolicy If the output is "TRUE," hardware-enforced DEP is available. To determine whether hardware-enforced DEP is available, follow these steps:Ĭlick Start, click Run, type cmd in the Open box, and then click OK.Īt the command prompt, type the following command, and then press ENTER: wmic OS Get DataExecutionPrevention_Available You can use the Wmic command-line tool to examine the DEP settings. To confirm that hardware DEP is working in Windows, use one of the following methods. However, depending on your configuration, hardware-enforced DEP may be disabled for 32-bit programs.įor information about how to configure memory protection in Windows XP with Service Pack 2, visit the following Microsoft Web site: How to confirm that hardware DEP is working in Windows In 64-bit versions of Windows, hardware-enforced DEP is always enabled for 64-bit native programs. Hardware-enforced DEP must be enabled for programs on the computer. Windows XP Media Center Edition 2005 and Microsoft Windows XP Tablet PC Edition 2005 include all the features and components of Windows XP SP2. The computer must have Windows XP with Service Pack 2 or Windows Server 2003 with Service Pack 1 installed.īoth 32-bit versions and 64-bit versions of Windows support hardware-enforced DEP. Depending on your computer manufacturer, the option to disable this support may be labeled "Data Execution Prevention," "XD," "Execute Disable," or "NX." On some computers, you can disable processor support for hardware-enforced DEP in the BIOS. Hardware-enforced DEP must be enabled in the BIOS. To determine whether your computer's processor supports hardware-enforced DEP, contact the manufacturer of your computer. This processor support may be known as NX (no-execute) or XD (execute disable) technology. Both Advanced Micro Devices (AMD) and Intel Corporation have defined and shipped Windows-compatible architectures that are compatible with DEP. Many recent processors support hardware-enforced DEP. The computer's processor must support hardware-enforced DEP. To use hardware-enforced DEP, you must meet all the following conditions: More information Requirements for using hardware-enforced DEP This article also describes how to confirm that hardware DEP is working in Windows. This article describes the requirements for using hardware-enforced DEP. DEP helps prevent these attacks by intercepting them and raising an exception. A type of malicious code attacks tries to insert and run code from non-executable memory locations. Hardware-enforced DEP marks all memory locations in a process as non-executable unless the location explicitly contains executable code. This article describes how to determine that hardware DEP is available and configured on your computer.Īpplies to: Windows Server 2012 R2, Windows 10 - all editions Original KB number: 912923 Introductionĭata Execution Prevention (DEP) is a set of hardware and software technologies that perform additional checks on memory to help protect against malicious code exploits.
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