Seokchan Yoon
Offensive Web Security Researcher
Security Contributor of GitHub, Python, Django, FastAPI(Starlette), Apache Airflow, Ruby, Ruby-on-Rails, Java Spring
Education
Bachelor's Degree in Computer Science & Engineering (Expected)
KyungHee University
Completed Vulnerability Analysis Track
Best of the Best, Korean Next-Generation Security Leader Training Program
Graduated from Dept. of Hacking Defense
Korea Digital Media Highschool
Work Experience
Security Researcher
Zellic.io USA
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Web2 systems and infrastructure security auditing
- Conducted in-depth security reviews of complex Web2 environments, including SaaS platforms and virtual asset exchange infrastructure
- Identified high-risk issues such as business logic flaws, denial-of-service, and SQL injection through white-box/gray-box testing
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Security consulting and risk management
- Worked directly with clients to propose and discuss optimal remediation plans that balance business continuity and security trade-offs
Security Team Member (Volunteer)
Airflow Security Team, Apache Software Foundation USA
- Reviewing and addressing security vulnerabilities in Apache Airflow
- Collaborating with the open-source community
- Maintaining the security posture of the project in accordance with ASF guidelines
Undergraduate Researcher
PWNLAB (Kyung Hee University System Security Lab, Advisor: Daehee Jang)
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Samsung multi-cloud integrated security verification tool development and web service penetration testing
- Implemented an IaC-based scanner that automatically diagnoses ~260 security compliance items across AWS, GCP, and Azure (IAM, Network, Container, Database, Storage, Monitoring, Logging, etc.) (Python, FastAPI)
- Designed an agentless architecture and multi-threaded parallel scan engine optimized for large-scale enterprise environments
- Performed black-box penetration testing for 19 Samsung-owned web services and identified 10 major vulnerabilities -- IDOR, file upload filter bypass, XSS, and other medium-impact issues with remediation guidance
- Maintained and developed features for the system hacking wargame `pwnable.kr` (PHP)
Unit [REDACTED], Private [REDACTED]
Research Institute under the Ministry of National Defense, Korea
- Research and development of [REDACTED]
R&D / Proactive Response Team, Security Engineer
STEALIEN
- Web penetration testing
- Development and operation of educational systems (Cyber Drill System, Django + React) and CTF
- Development and maintenance of internal tools, technical blogs, deployment systems, and other infrastructure
CTF Awards
CCE (Cyber Conflict Exercise)
General Division
hosted by National Intelligence Service, Korea
Team: 경희대미남해커들 (KHU's hansome hackers)
DEF CON CTF 33
hosted by Nautilus Institute
Team: Cold Fusion
🏆 White Hat Contest
Soldier Division
hosted by Ministry of National Defense, Korea
Team: 키보드워리어플랫폼 (Keyboard Warrior Platform)
Korea Defense Minister Award
CODEGATE
University Division
hosted by Ministry of Science and ICT, Korea
Team: 경희대미남해커들 (KHU's hansome hackers)
CODEGATE
University Division
hosted by Ministry of Science and ICT, Korea
Team: 경희대미남해커들 (KHU's hansome hackers)
🏆 CCE (Cyber Conflict Exercise)
Public Institution Sector Division
hosted by National Intelligence Service, Korea
Team: resilience
Korea Security Research Institute Director Award
🏆 HACKTHEON SEJONG National University Cybersecurity Competition
hosted by Sejong Special Self-Governing City, Korea
Team: 라임도둑 (Lime Thief)
Korea Security Research Institute Director Award
🏆 CCE (Cyber Conflict Exercise)
Public Institution Sector Division
hosted by National Intelligence Service, Korea
Team: resilience
Korea Security Research Institute Director Award
🏆 Cyber Operations Challenge
Student Division
hosted by Ministry of National Defense, Korea
Team: 윤석찬TV구독과좋아요알림설정까지
Korea Cyber Command Award
🏆 Cybersecurity Competition
Individual Preliminary Round
hosted by Ministry of Education, Korea
SWU President Award
🏆 Cybersecurity Competition
Team Finals
hosted by Ministry of Education, Korea
Team: 문시우1인팀 (munsiwoo 1-person team)
Education Minister Award
🏆 Cybersecurity Competition
Team Finals
hosted by Korea Education and Research Information Service
Team: 4-day exploit
KERIS Director Award
Disclosed Vulnerabilities
Django
10
Apache Airflow
3
NAVER
3
Ruby on Rails
2
Python
1
FastAPI / Starlette
1
Ruby
1
Java Spring
1
GitHub
1
CVE-2024-7592
Denial of ServiceQuadratic complexity parsing cookies with backslashes
There is a LOW severity vulnerability affecting CPython, specifically the 'http.cookies' standard library module. When parsing cookies that contained backslashes for quoted characters in the cookie value, the parser would use an algorithm with quadratic complexity, resulting in excess CPU resources being used while parsing the value.
CVE-2023-36053
Regular Expression Denial of ServicePotential regular expression denial of service vulnerability in EmailValidator/URLValidator
In Django 3.2 before 3.2.20, 4 before 4.1.10, and 4.2 before 4.2.3, EmailValidator and URLValidator are subject to a potential ReDoS (regular expression denial of service) attack via a very large number of domain name labels of emails and URLs.
CVE-2024-24680
Denial of ServicePotential denial-of-service in intcomma template filter
An issue was discovered in Django 3.2 before 3.2.24, 4.2 before 4.2.10, and Django 5.0 before 5.0.2. The intcomma template filter was subject to a potential denial-of-service attack when used with very long strings.
CVE-2024-27351
Regular Expression Denial of ServicePotential regular expression denial-of-service in django.utils.text.Truncator.words()
In Django 3.2 before 3.2.25, 4.2 before 4.2.11, and 5.0 before 5.0.3, the django.utils.text.Truncator.words() method (with html=True) and the truncatewords_html template filter are subject to a potential regular expression denial-of-service attack via a crafted string. NOTE: this issue exists because of an incomplete fix for CVE-2019-14232 and CVE-2023-43665.
CVE-2024-21520
Cross-Site ScriptingCross-Site Scripting (XSS) in browserable API of django-rest-framework
Versions of the package djangorestframework before 3.15.2 are vulnerable to Cross-site Scripting (XSS) via the break_long_headers template filter due to improper input sanitization before splitting and joining with <br> tags.
CVE-2024-41991
Denial of ServicePotential denial-of-service vulnerability in django.utils.html.urlize() and AdminURLFieldWidget
An issue was discovered in Django 5.0 before 5.0.8 and 4.2 before 4.2.15. The urlize and urlizetrunc template filters, and the AdminURLFieldWidget widget, are subject to a potential denial-of-service attack via certain inputs with a very large number of Unicode characters.
CVE-2024-53908
SQL InjectionPotential SQL injection in HasKey(lhs, rhs) on Oracle
An issue was discovered in Django 5.1 before 5.1.4, 5.0 before 5.0.10, and 4.2 before 4.2.17. Direct usage of the django.db.models.fields.json.HasKey lookup, when an Oracle database is used, is subject to SQL injection if untrusted data is used as an lhs value. (Applications that use the jsonfield.has_key lookup via __ are unaffected.)
CVE-2025-48432
Log InjectionPotential log injection via unescaped request path
An issue was discovered in Django 5.2 before 5.2.3, 5.1 before 5.1.11, and 4.2 before 4.2.23. Internal HTTP response logging does not escape request.path, which allows remote attackers to potentially manipulate log output via crafted URLs. This may lead to log injection or forgery when logs are viewed in terminals or processed by external systems.
CVE-2025-64458
Denial of ServicePotential denial-of-service vulnerability in HttpResponseRedirect and HttpResponsePermanentRedirect on Windows
NFKC normalization in Python is slow on Windows. As a consequence, django.http.HttpResponseRedirect, django.http.HttpResponsePermanentRedirect, and the shortcut django.shortcuts.redirect were subject to a potential denial-of-service attack via certain inputs with a very large number of Unicode characters.
CVE-2025-64460
Denial of ServicePotential denial-of-service vulnerability in XML serializer text extraction
Algorithmic complexity in django.core.serializers.xml_serializer.getInnerText() allows a remote attacker to cause a potential denial-of-service attack triggering CPU and memory exhaustion via specially crafted XML input processed by the XML Deserializer.
CVE-2026-1285
Denial of ServicePotential denial-of-service vulnerability in django.utils.text.Truncator HTML methods
django.utils.text.Truncator.chars() and Truncator.words() methods (with html=True) and the truncatechars_html and truncatewords_html template filters allow a remote attacker to cause a potential denial-of-service via crafted inputs containing a large number of unmatched HTML end tags.
CVE-2025-62727
Denial of ServiceStarlette vulnerable to O(n^2) DoS via Range header merging
An unauthenticated attacker can send a crafted HTTP Range header that triggers quadratic-time processing in Starlette's FileResponse Range parsing/merging logic. This enables CPU exhaustion per request, causing denial-of-service for endpoints serving files (e.g., StaticFiles or any use of FileResponse).
CVE-2024-39877
Code ExecutionApache Airflow: DAG Author Code Execution possibility in airflow-scheduler
Apache Airflow 2.4.0, and versions before 2.9.3, has a vulnerability that allows authenticated DAG authors to craft a doc_md parameter in a way that could execute arbitrary code in the scheduler context, which should be forbidden according to the Airflow Security model.
CVE-2024-39863
Cross-Site ScriptingApache Airflow: Potential XSS Vulnerability
Apache Airflow versions before 2.9.3 have a vulnerability that allows an authenticated attacker to inject a malicious link when installing a provider.
CVE-2024-45034
Code ExecutionApache Airflow: Authenticated DAG authors could execute code on scheduler nodes
Apache Airflow versions before 2.10.1 have a vulnerability that allows DAG authors to add local settings to the DAG folder and get it executed by the scheduler, where the scheduler is not supposed to execute code submitted by the DAG author.
CVE-2024-41123
Denial of ServiceDoS vulnerabilities in REXML
The REXML gem before 3.3.2 has some DoS vulnerabilities when it parses an XML that has many specific characters such as whitespace character, >] and ]>.
CVE-2024-47887
Regular Expression Denial of ServicePossible ReDoS vulnerability in HTTP Token authentication in Action Controller
There is a possible ReDoS vulnerability in Action Controller's HTTP Token authentication. For applications using HTTP Token authentication via authenticate_or_request_with_http_token or similar, a carefully crafted header may cause header parsing to take an unexpected amount of time, possibly resulting in a DoS vulnerability.
CVE-2024-41128
Regular Expression Denial of ServicePossible ReDoS vulnerability in query parameter filtering in Action Dispatch
There is a possible ReDoS vulnerability in the query parameter filtering routines of Action Dispatch. Carefully crafted query parameters can cause query parameter filtering to take an unexpected amount of time, possibly resulting in a DoS vulnerability.
CVE-2024-38809
Denial of ServiceSpring Framework DoS via conditional HTTP request
Applications that parse ETags from "If-Match" or "If-None-Match" request headers are vulnerable to DoS attack.
HackerOne #2646500
Denial of ServiceDoS Vulnerability in GitHub Enterprise
GitHub and GitHub Enterprise are vulnerable to a potential denial-of-service attack caused by a maliciously crafted HTTP request.
NBB-1126
Stored XSSStored XSS
NAVER is vulnerable to a stored-xss caused by a crafted payload.
NBB-1143
SQL InjectionSQL Injection
NAVER is vulnerable to a SQL injection caused by a crafted payload.
NBB-1260
Stored XSSStored XSS
NAVER is vulnerable to a stored XSS caused by a crafted payload.
Talks
“Django Framework from a Hacker's Perspective” (in Korean)
PyCon KR 2024
“Analysis of Django Framework N-day Vulnerabilities and Secure Coding Guide” (in Korean)
CODEGATE 2023
“Django Framework 1-day Analysis” (in Korean)
26th Hacking Camp
“Bug Cases and Secure Coding in Modern Web Services” (in Korean)
STEALIEN Security Seminar
Blog Posts
How I Found a $2,163 Vulnerability with a $5 Prompt
https://new-blog.ch4n3.kr/llm-found-security-issues-from-django-en/
DEF CON 33 CTF Review
https://new-blog.ch4n3.kr/def-con-33-review-en/
Is Airflow Truly Safe? ー With Reviews of Disclosed Vulnerabilities
https://new-blog.ch4n3.kr/is-airflow-truly-safe-en/
Your Django App Is Vulnerable to DoS Attacks: Update Your Python Version Now
https://new-blog.ch4n3.kr/cve-2024-7592-en/
Review for Recent Django Security Issues - CVE-2024-24680, CVE-2024-27351
https://new-blog.ch4n3.kr/reviews-for-2024-django-security-issues/
Do not use `maildev` anyway 💣
https://new-blog.ch4n3.kr/do-not-use-maildev-anyway/