DEF CON CTF Qualifier 2025
44 challenges with 42 published community solutions between them. Solution links go to CTFtime’s task page, which aggregates every writeup for a challenge - individual blog posts rot, the aggregator does not. 14 of them also carry the solution DEF CON CTF Qualifier 2025’s own organisers published, which is linked on the challenge itself.
Full task list on CTFtimeUncategorised42
The upstream scoreboard did not say, so neither do we.
Published by the organisers in Nautilus-Institute/quals-2025: README.md, solver/src/chall_rng.cpp, solver/src/chall_rng.hpp, solver/src/deck.cpp, solver/src/deck.hpp, solver/src/main.cpp
Also written up in: CUCTF/ctf-writeups, Hope0351/CTF-collection, pawel-kojma/ctf-writeups, CUCTF/ctf-writeups, Hope0351/CTF-collection
Published by the organisers in Nautilus-Institute/quals-2025: solver/deck.cpp, solver/deck.hpp, solver/main.cpp
Also written up in: CUCTF/ctf-writeups, Hope0351/CTF-collection, CUCTF/ctf-writeups, Hope0351/CTF-collection
Published by the organisers in Nautilus-Institute/quals-2025: README.md, solver/src/chall_rng.cpp, solver/src/chall_rng.hpp, solver/src/deck.cpp, solver/src/deck.hpp, solver/src/main.cpp
Published by the organisers in Nautilus-Institute/quals-2025: solver/readme.md, solver/make_jxl.py, solver/part_1.jxl.txt, solver/part_2.jxl.txt, solver/png_to_hex.py, solver/solve.py
Published by the organisers in Nautilus-Institute/quals-2025: solver/offline_solver_server.py, solver/offline_solver.py, solver/sol1.rs, solver/solver.py
Published by the organisers in Nautilus-Institute/quals-2025: solver/readme.md, solver/app_exp/exp.sh, solver/solve.py
Also written up in: Nautilus-Institute/finals-2025, Nautilus-Institute/finals-2025
Youwouldntdownloada3dprinter
2 official solutionsAlso written up in: Thitav/ctf-writeups, Thitav/ctf-writeups
2025 04 25
1 official solutionAlso written up in: imp.ress.me
Also written up in: Nautilus-Institute/finals-2025
Auction Server
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
CLAUDE
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Coordinator
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Also written up in: Nautilus-Institute/finals-2025
Also written up in: yPin9/CTF-Writeup
Also written up in: yPin9/CTF-Writeup
Also written up in: Nautilus-Institute/finals-2025
Fun with sine waves
1 official solutionAlso written up in: zackorndorff.com
Also written up in: Nautilus-Institute/finals-2025
Also written up in: Nautilus-Institute/finals-2025
Published by the organisers in Nautilus-Institute/quals-2025: solver.py
Investigating V8 Garbage Collector
1 official solutionAlso written up in: ouuan.moe
Jukebooox
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Laptooop
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Also written up in: Nautilus-Institute/finals-2025
Published by the organisers in Nautilus-Institute/quals-2025: solver/solver.py
Published by the organisers in Nautilus-Institute/quals-2025: solver/flag_3.cpp
Nilua
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Also written up in: Nautilus-Institute/finals-2025
Published by the organisers in Nautilus-Institute/quals-2025: solver/solver.py
Published by the organisers in Nautilus-Institute/quals-2025: solver/solver.py
Poller
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Published by the organisers in Nautilus-Institute/quals-2025: solver/solver.rb
Also written up in: Nautilus-Institute/finals-2025
Also written up in: blog.cloudlabs.ufscar.br
Also written up in: Nautilus-Institute/finals-2025
Stb Ds
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Test Upload
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Vibe1
1 official solutionAlso written up in: satoki/ctf_writeups
Water Pollution
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Xor Str
1 official solutionAlso written up in: Nautilus-Institute/finals-2025
Published by the organisers in Nautilus-Institute/quals-2025: solver.py
Reverse engineering1
Work out what a compiled program does without its source, then work backwards from the check to the input that passes it.
Published by the organisers in Nautilus-Institute/quals-2025: src/solver.c
- reverse
Same technique in picoCTF: Checkpass, WinAntiDbg0x100, WinAntiDbg0x200
Misc1
Everything that fits no other box: esolangs, puzzles, scripting exercises, and the jail escapes that have not yet earned their own category.
rainbow mountain
1 writeupSame technique in picoCTF: PW Crack 2, Permissions, Specialer