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Daily AlpacaHack

A daily CTF challenge with a fun new puzzle every day

What is Daily AlpacaHack?

We publish one simple, beginner-friendly or educational CTF challenge every day!

Join Anytime

Solve within 24 hours of release to appear on the leaderboard.

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Discussion with friends or AI is welcome (account sharing is prohibited).

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Sharing solutions is allowed only after 24 hours have passed since release.

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Today's Challenge
kanonkanon
honk the klaxon
Crypto
Medium
35 solves
Submissions (latest 3)
kowerkoint
kowerkoint

SOLVED!

Jun 24, 6:58 AM

pppp4649

SOLVED!

Jun 24, 5:08 AM

Leaderboard

Try the first challenge

Is this your first CTF? Let's begin by tackling the first challenge released on Daily AlpacaHack.

View challenge
admin
AlpacaHack 2100
Misc
Welcome🌱
1,909 solves
Upcoming challenges reveal the , , and in advance.
Prev

Jun 2026

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Upcoming
Mon
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Wed
Thu
Fri
Sat
Sun
1
admin
Half-Year Recap
Misc
Welcome🌱
237 solves
2
minaminaominaminao
Cache Me If You Can
Web
Easy🌱
199 solves
3
minaminaominaminao
vm1
Misc
Medium
95 solves
4
pppp4649pppp4649
Small e
Crypto
Easy🌱
134 solves
5
minaminaominaminao
RPS GAME
Misc
Crypto
Medium
96 solves
6
nozokare
Flag for localhost
Web
Easy🌱
156 solves
7
tan90909090tan90909090
C++ flag checker
Rev
Hard
84 solves
8
shiragishiragi
Guess IP
Misc
Easy🌱
140 solves
9
nozokare
A Piece of DHKE
Crypto
Medium
81 solves
10
shiragishiragi
chmod-swapper
Misc
Medium
84 solves
11
tchentchen
Alpaca Certification
Web
Easy🌱
155 solves
12
rsk0315
Floating Equality
Misc
Medium
89 solves
13
pppp4649pppp4649
Elliptic Equation
Crypto
Hard
59 solves
14
tchentchen
CAuth
Web
Hard
65 solves
15
minaminaominaminao
SITE/2
Web
Easy🌱
117 solves
16
tan90909090tan90909090
Xored PNG
Misc
Medium
84 solves
17
tchentchen
Looks like Alpacahack
Web
Medium
80 solves
18
shiragishiragi
Catrunner 2
Misc
Easy🌱
103 solves
19
minaminaominaminao
Flag Printer 20XX
Misc
Medium
61 solves
20
nozokare
xorshift521
Crypto
Hard
54 solves
21
k0080k0080
what-is-my-size
Pwn
Hard
63 solves
22
minaminaominaminao
✌️✌️✌️
Crypto
Easy🌱
84 solves
23
tchentchen
Secret Renderer
Web
Medium
69 solves
24
kanonkanon
honk the klaxon
Crypto
Medium
35 solves
25
colza
Planned topicArchive
Misc
Easy🌱
26
Coming soon
28
Planned topicTBA
Pwn
Hard
29
Coming soon
30
Coming soon
2
Planned topicMathematics
Crypto
Easy🌱
3
Coming soon
4
Coming soon
5
Coming soon

Want a harder challenge?

Go to B-SIDE

Writeups

Daily AlpacaHackに挑戦するつくよみちゃん 06/23/Secret Renderer/tchen

tsukuyomi-chan

ja
Secret Renderer

15 hours ago

minaminao

Writeup for ✌️✌️✌️

author
ja

2026/06/22 17:14

Daily AlpacaHackに挑戦するつくよみちゃん 06/22/✌️✌️✌️/minaminao

tadanobutubutu

Writeup for ✌️✌️✌️

tadanobutubutu

Writeup for what-is-my-size

Daily AlpacaHackに挑戦するつくよみちゃん 06/20/xorshift521/nozokare

ja

2026/06/20 15:40

Rows:

Log Viewer

Topic: Remote Code ExecutionReleased: Dec 22, 2025

241 solves
Web
Medium5.0

by

tchen

tchen

Simple log viewer with regex feature.

Beginner Hint: What is an instance spawner?
  • In CTFs, some challenges require dynamically creating a separate challenge server for each player (or team).
  • For example, if a player can change the state of a challenge server, it may affect other players.
  • To handle such issues, an instance spawner is provided.
  • On AlpacaHack, clicking the "Spawn Challenge Server" button automatically creates an isolated challenge server for each user.
  • This challenge also uses an instance spawner.
  • To help reduce server load, please try to solve the challenge locally before spawning.
  • Note that on Daily AlpacaHack, even for challenges that do not require an instance spawner, the challenge server may be stopped after some time has passed since release, and the "Spawn Challenge Server" button will then appear.
Beginner Hint: The Starting Point of the Attack
  • The goal of this challenge is to read the flag file located in the root directory.
  • The starting point for achieving this is an OS command injection in the query part of the awk command.
Beginner Hint: Pitfalls in Payload Construction
  • In Python, subprocess.run method executes commands without going through a shell like Bash.
  • As a result, you cannot split commands using ; or perform command substitution with $(command).
log-viewer.tar.gz

Please sign in to submit the flag.

descriptionsolveswriteups