Hamiltonian Path

Platform GPN CTF 2026 (kitctf) Difficulty Mixed (Easy → Hard) OS Jeopardy — Reverse, Crypto, Web, Pwn, Misc Tags AVX2 lane-swap miscompilation discovery + Kannan-embedding SIS lattice attack, NTRU mod-q reduction bug (c mod p == m), ECDSA nonce reuse from MD5(uuid3) collisions via fastcoll, eBPF signed-comparison verifier bypass with patched bzImage, JVM AOT cache override of bytecode, PHP 7.4 PHAR deserialization across two TCP races, Pydantic ForwardRef eval in create_model, CSS attribute-selector cookie exfiltration through Link: rel=stylesheet, holpy proof-checker thm re-axiomatization, knitout front/back-bed bitmap, ternary amplitude-modulated UART, Hamiltonian path on 250-node FSM extracted from jump tables, RFC 5424 syslog stream demux, Rust setuid TOCTOU symlink swap GPN CTF 2026 is the Gulaschprogrammiernacht CTF hosted annually by KITCTF at the GPN hacker camp in Karlsruhe, Germany. The 2026 edition runs a Jeopardy board across reverse engineering, crypto, web, pwn, and misc, with a sharp lean toward low-level systems bugs — a missing mod q in an NTRU implementation, a 4-way AVX2 lane-swap in a gcc -O3 -mavx2 build, a deleted BPF_ADJ_END_FROM_* check in a custom kernel, a JVM AOT cache that silently overrides a JAR method. The flavour throughout is kitchen — recipes, ovens, pots — and the flags universally read like Bavarian beer-tent slogans. ...

Platform GPN CTF 2026 (kitctf) Difficulty Medium-Hard OS Reverse — 250-state FSM, jump tables, Hamiltonian path Tags reading 4,500 lines of straight-line dispatch in Binja HLIL instead of objdump, using Stack View to identify a per-state visit-counter array, extracting jump-table successors via function.basic_blocks[i].outgoing_edges, building a 250-node directed graph from Binja-recovered edges, running Warnsdorff's heuristic DFS to find a Hamiltonian path in ~70 ms Königsberg Delivery Problem is the GPN CTF 2026 reverse challenge that turned a 4,500-line straight-line dispatch routine into a graph-theory problem. The binary cartographer is 140 KB, not stripped, dynamically linked, x86-64 PIE. The interesting function cfg() is 250 logically-identical state blocks ending in indirect jmp rdx jumps over .rodata jump tables. The win condition is “visit every state at least once” — Hamiltonian path on a 250-node directed graph. ...