Taeyang Lee

About Me

I am Taeyang Lee, a senior security researcher at Theori. I usually use @5unkn0wn as my online handle.

I work on vulnerability research, exploit development, reverse engineering, and security assessment. I especially enjoy reverse engineering: taking systems apart, understanding how they work internally, and using that understanding to find interesting bugs.

My recent research focuses on Linux kernel and Android bootloader security. I am also interested in binary obfuscation, deobfuscation, and devirtualization.

I played CTFs with The Duck and MMM.

Research

Copy Fail - CVE-2026-31431
- A Linux kernel local privilege escalation vulnerability that turns a 4-byte scratch write into a controlled file-backed page-cache overwrite.
- Chained an authencesn scratch-write bug with AF_ALG and splice().
Linux Kernel / Kernel CTF
- CVE-2026-23060 - An out-of-bounds vulnerability in crypto/authencesn.
  - Kernel CTF lts-6.12.62 / cos-121-18867.294.66 / mitigation-v4-6.12
- CVE-2026-52910 - bpf: Free reuseport cBPF prog after RCU grace period.
  - Kernel CTF lts-6.12.79 / cos-121-18867.381.45 / mitigation-v4-6.12
Android Bootloader
- Researched Android bootloader vulnerabilities in Samsung Odin.
- CVE-2024-20880 - Stack-based buffer overflow in bootloader.
- CVE-2024-20882 - Out-of-bounds read in bootloader.
Deobfuscation
- Analyzed commercial and Android obfuscation systems, including Themida and VMProtect virtualized code.
- Code Defender deobfuscation
- Internal research on Themida / VMProtect deobfuscation and devirtualization.

Work Experience

Senior Security Researcher
Theori, 2019.01 - Present
- Vulnerability research / Exploit development
- Security assessment / Penetration testing
- Binary and mobile application analysis
Researcher
Stealien, 2018.03 - 2018.12
- Penetration testing
- Ransomware analysis

Awards

I listed CTFs and competitions where I made meaningful contributions.

DEF CON CTF, 1st place, MMM, 2025, 2024, 2023, 2022
Google CTF, 1st place, MMM, 2023
Codegate CTF, 1st place, The Duck, 2022
LINE CTF, 1st place, The Duck, 2025 / 2024 / 2023 / 2021

Show all awards

2025	1st	PoC CTF Individual	5unkn0wn	Seoul, South Korea
2025	1st	LINE CTF	The Duck	Japan
2025	3rd	CODEGATE General	The Duck	Seoul, South Korea
2025	1st	Cyber Conflict Exercise	The Mallard Duck	Seoul, South Korea
2025	1st	DEF CON 33	MMM	Las Vegas, US
2025	1st	Remedy CTF	Chainlight	N/A
2024	3rd	HITCON CTF 2024	MMM	Taipei, Taiwan
2024	1st	Cyber Conflict Exercise	The Duckling	Seoul, South Korea
2024	1st	DEF CON 32	MMM	Las Vegas, US
2024	1st	ACSC CTF	5unkn0wn	Asia International
2024	1st	LINE CTF	The Duck	Japan
2023	1st	DEF CON 31	MMM	Las Vegas, US
2023	1st	Google CTF	MMM	N/A
2023	1st	Whitehat Contest	The Duck	Seoul, South Korea
2023	1st	LINE CTF	The Duck	Japan
2023	1st	Samsung SSTF	The Duck	Seoul, South Korea
2023	2nd	Blackhat MEA	The Duck	Riyadh, Saudi Arabia
2023	2nd	WACON	The Duck	Seoul, South Korea
2023	2nd	Cyber Conflict Exercise	The Duck	Seoul, South Korea
2023	3rd	CODEGATE General	The Duck	Seoul, South Korea
2022	1st	DEF CON 30	MMM	Las Vegas, US
2022	1st	CODEGATE General	The Duck	Seoul, South Korea
2022	1st	Cyber Conflict Exercise	The Duck	Seoul, South Korea
2022	1st	Samsung SSTF	The Duck	South Korea
2022	2nd	Whitehat Contest	Kang-Jinoh fc	South Korea
2022	2nd	WACON	The Duck	Seoul, South Korea
2021	1st	Whitehat Contest	Kang-Jinoh fc	South Korea
2021	1st	Samsung SSTF	The Duck	South Korea
2021	1st	LINE CTF	The Duck	Japan
2021	3rd	Cyber Conflict Exercise	Dream Retriever	South Korea
2020	1st	Samsung SSTF	The Duck	Seoul, South Korea
2020	1st	Whitehat Grand Prix 06	KingTigerPrawn	Vietnam
2020	1st	Cyber Conflict Exercise	SpaceX Rocket	Seoul, South Korea
2020	1st	Digital Forensic Challenge	noname	Seoul, South Korea
2019	1st	Cyber Conflict Exercise	Yook-Hae-Gong	Busan, South Korea
2019	1st	Digital Forensic Challenge	noname	Seoul, South Korea
2018	2nd	Whitehat Grand Prix 04	coconutCoffee	Hanoi, Vietnam
2018	2nd	Digital Forensic Challenge	Foreng2	Seoul, South Korea
2018	2nd	Cyber Conflict Exercise	LeaveCat	Jeju, South Korea
2017	3rd	CODEGATE Junior	5unkn0wn	Seoul, South Korea
2016	1st	Whitehat Contest Junior	HackCat	Seoul, South Korea
2016	2nd	CODEGATE Junior	5unkn0wn	Seoul, South Korea

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