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hidden instructions

4 articles · Page 1 of 1
Black & White Path
Black & White Path
Jun 6, 2026 · Information Security

The Secret CPU Instructions Intel, AMD and ARM Keep Hidden (And Why They Matter)

The article explores the origins of undocumented CPU instructions—from early transistor‑saving tricks like SALC and POP CS to modern hidden backdoors such as Intel’s undocumented RISC core and the udbgrd/udbgwr commands—explaining how researchers like 0day_ninja use the MystFuzz tool to discover and exploit these covert opcodes.

CPUMystFuzzhardware security
0 likes · 8 min read
The Secret CPU Instructions Intel, AMD and ARM Keep Hidden (And Why They Matter)
Java Tech Enthusiast
Java Tech Enthusiast
Jun 9, 2024 · Information Security

Exploring Hidden x86 CPU Instructions and Their Security Implications

The article investigates undocumented x86 opcodes, describing a depth‑first search that uses page‑faults to locate hidden instruction boundaries, and reports finding dozens of executable but undocumented instructions on Intel and AMD CPUs, highlighting potential security risks and the need for vigilant hardware analysis.

AssemblyCPUhidden instructions
0 likes · 9 min read
Exploring Hidden x86 CPU Instructions and Their Security Implications
Liangxu Linux
Liangxu Linux
May 12, 2022 · Information Security

Do CPUs Hide Secret Instructions? Uncovering the Dark Corners of the x86 ISA

This article explores whether modern CPUs contain undocumented or hidden instructions, explains the challenges of searching the variable‑length x86 ISA, presents a depth‑first algorithm that skips irrelevant bytes, shows how to infer instruction length using page‑fault side‑effects, and reveals discovered hidden opcodes on Intel and AMD processors.

CPUInstruction Sethidden instructions
0 likes · 10 min read
Do CPUs Hide Secret Instructions? Uncovering the Dark Corners of the x86 ISA
IT Services Circle
IT Services Circle
Apr 15, 2022 · Information Security

Exploring Hidden x86 CPU Instructions and Their Security Implications

The article investigates whether modern x86 CPUs contain undocumented or hidden instructions, explains how to search the instruction space using a depth‑first algorithm that leverages page‑fault side‑effects to determine instruction length, and presents the results of uncovering such hidden opcodes on Intel and AMD processors, highlighting the potential security risks.

CPUhidden instructionsreverse engineering
0 likes · 11 min read
Exploring Hidden x86 CPU Instructions and Their Security Implications