ctf-pwn

name ctf-pwn description Provides binary exploitation techniques for CTF challenges. Use when you already have a vulnerable native target or service and need to turn memory corruption or low-level primitives into code execution or privilege escalation, such as buffer overflows, format strings, heap bugs, ROP, ret2libc, shellcode, kernel exploitation, seccomp bypass, sandbox escape, or Windows/Linux exploit chains. Do not use it when the main blocker is understanding what the binary does; use reverse engineering first. Do not use it for pure web bugs, disk or packet forensics, or standalone crypto/math challenges. license MIT compatibility Requires filesystem-based agent (Claude Code or similar) with bash, Python 3, and internet access for tool installation. allowed-tools Bash Read Write Edit Glob Grep Task WebFetch WebSearch metadata {"user-invocable":"false"} CTF Binary Exploitation (Pwn) Quick reference for binary exploitation (pwn) CTF challenges. Each technique has a one-liner here; see supporting files for full details. Prerequisites Python packages (all platforms): pip install pwntools ropper ROPgadget Linux (apt): apt install gdb binutils strace ltrace qemu-system-x86 macOS (Homebrew): brew install gdb binutils qemu Ruby gems (all platforms): gem install one_gadget seccomp-tools Manual install: pwndbg — Linux: GitHub , macOS: brew install pwndbg/tap/pwndbg-gdb checksec — included with pwntools Additional Resources overflow-basics.md - Stack/global buffer overflow, ret2win, canary bypass, canary byte-by-byte brute force on forking servers, struct pointer overwrite, signed integer bypass, hidden gadgets, stride-based OOB read leak, parser stack overflow via unchecked memcpy length with callee-saved register restoration rop-and-shellcode.md - Core ROP chains (ret2libc, syscall ROP, rdx control, shell interaction), ret2csu, bad character XOR bypass, exotic x86 gadgets (BEXTR/XLAT/STOSB/PEXT), stack pivot via xchg rax,esp, sprintf() gadget chaining for bad character bypass, canary XOR epilogue as RDX zeroing gadget, stub_execveat syscall as execve alternative via read() return value rop-advanced.md - Advanced ROP techniques: double stack pivot to BSS via leave;ret, SROP (Sigreturn-Oriented Programming) with UTF-8 constraints, seccomp bypass, RETF architecture switch (x64→x32) for seccomp bypass, shellcode with input reversal, .fini_array hijack, ret2vdso, pwntools template, x32 ABI syscall aliasing for seccomp bypass, time-based blind shellcode exfiltration format-string.md - Format string exploitation (leaks, GOT overwrite, blind pwn, filter bypass, canary leak, __free_hook, .rela.plt patching, saved EBP overwrite for .bss pivot, argv[0] overwrite for stack smash info leak, .fini_array loop for multi-stage exploitation, __printf_chk bypass with sequential %p, single-call leak + GOT overwrite, ROT13-encoded format string exploit through input transformation) advanced.md - Seccomp advanced techniques, UAF, JIT, esoteric GOT, heap overlap via base conversion, tree data structure stack underallocation, ret2dlresolve, kernel exploitation (basic) heap-techniques.md - House of Apple 2 (+ setcontext SUID variant), House of Einherjar, House of Orange/Spirit/Lore/Force, heap grooming, custom allocators (nginx, talloc), classic unlink, musl libc heap (meta pointer + atexit hijack), tcache stashing unlink attack, unsafe unlink + top chunk consolidation heap-techniques-2.md - CTF-writeup heap variants: UAF vtable pointer encoding shell argument, uninitialized chunk residue pointer leak, tcache strcpy null-byte overflow + backward consolidation, adjacent-struct fn-pointer overflow for libc leak + GOT overwrite, hidden-menu tcache poisoning, tcache double-free + fake _IO_FILE vtable stdout hijack, tcache-to-fastbin promotion cross-bin attack, 6-bit index OOB + written_bytes accumulator, IS_MMAPED bit-flip for unsorted bin leak on calloc'd chunk, filename-regex-constrained fastbin via LSB-only heap pointer overwrite, custom allocator unsafe unlink to GOT heap-fsop.md - FILE-structure (_IO_FILE) exploitation: fastbin stdout vtable two-stage hijack for PIE + Full RELRO, _IO_buf_base null-byte stdin hijack, glibc 2.24+ _IO_FILE vtable validation bypass, unsorted-bin attack on stdin IO_buf_end, unsorted-bin corruption via mp structure, realloc(ptr, 0) as free() UAF, single-byte reference counter wraparound UAF advanced-exploits.md - Advanced exploit techniques (part 1): VM signed comparison, BF JIT shellcode, type confusion, off-by-one index corruption, DNS overflow, ASAN shadow memory, format string with encoding constraints, custom canary preservation, signed integer bypass, canary-aware partial overflow, CSV injection, MD5 preimage gadgets, VM GC UAF slab reuse, path traversal sanitizer bypass, FSOP + seccomp bypass via openat/mmap/write advanced-exploits-2.md - Advanced exploit techniques (part 2): bytecode validator bypass via self-modification, io_uring UAF with SQE injection, integer truncation int32->int16, GC null-reference cascading corruption, leakless libc via multi-fgets stdout FILE overwrite, signed/unsigned char underflow heap overflow, XOR keystream brute-force write primitive, tcache pointer decryption heap leak, unsorted bin promotion via forged chunk size, FSOP stdout TLS leak, TLS destructor hijack via __call_tls_dtors , custom shadow stack pointer overflow bypass, signed int overflow negative OOB heap write, XSS-to-binary pwn bridge advanced-exploits-4.md - Advanced exploit techniques (part 4): Windows SEH overwrite + pushad VirtualAlloc ROP, IAT-relative resolution, detached process shell stability, SeDebugPrivilege SYSTEM escalation, ARM buffer overflow with Thumb shellcode, Forth interpreter system word exploitation, GF(2) Gaussian elimination for multi-pass tcache poisoning, single-bit-flip exploitation primitive (mprotect + iterative code patching), Game of Life shellcode evolution via still-lifes, UAF via menu-driven strdup/free ordering, Windows CFG bypass via system() as valid call target, neural network output as function pointer index OOB, shellcode unique-byte limit bypass via counter overflow advanced-exploits-3.md - Advanced exploit techniques (part 3): stack variable overlap / carry corruption OOB, 1-byte overflow via 8-bit loop counter, game AI arithmetic mean OOB read, arbitrary read/write GOT overwrite to shell, stack leak via __environ + memcpy overflow, JIT sandbox escape via uint16 jump truncation, DNS compression pointer stack overflow with multi-question ROP, ELF code signing bypass via program header manipulation, game level format signed/unsigned coordinate mismatch, file descriptor inheritance via missing O_CLOEXEC, sign extension integer underflow in metadata parsing, ROP chain construction with read-only primitive, 4-byte shellcode with timing side-channel via persistent registers, CRC oracle as arbitrary read, UTF-8 case conversion buffer overflow advanced-exploits-5.md - Advanced exploit techniques (part 5): data-interpretation exploitation — Chip-8 emulator OOB memory for ret2libc, double-precision float quicksort canary repositioning, bloom filter abs(INT_MIN) negative index OOB write sandbox-escape.md - Custom VM exploitation, FUSE/CUSE devices, busybox/restricted shell, shell tricks, process_vm_readv sandbox bypass, named pipe file size bypass, CPU emulator print opcode Python eval injection (cross-references ctf-misc/pyjails.md for Python jail techniques) kernel.md - Linux kernel exploitation fundamentals: environment setup, QEMU debug, heap spray structures (tty_struct, poll_list, user_key_payload, seq_operations), kernel stack overflow, canary leak, privilege escalation (ret2usr, kernel ROP), modprobe_path overwrite, core_pattern overwrite, kmalloc size mismatch heap overflow + struct file f_op corruption kernel-techniques.md - Kernel exploitation techniques: tty_struct kROP (fake vtable + stack pivot), AAW via ioctl register control, userfaultfd race stabilization, SLUB allocator internals (freelist hardening/obfuscation), leak via kernel panic, MADV_DONTNEED race window extension (DiceCTF 2026), cross-cache CPU-split attack (DiceCTF 2026), PTE overlap file write (DiceCTF 2026), addr_limit bypass via failed file open for kernel memory read/write kernel-bypass.md - Kernel protection bypass: KASLR/FGKASLR bypass (__ksymtab), KPTI bypass (swapgs trampoline, signal handler, modprobe_path/core_pattern via ROP), SMEP/SMAP bypass, GDB kernel module debugging, initramfs/virtio-9p workflow, exploit templates, exploit delivery field-notes.md - Detailed pwn notes: heap exploitation quick reference, additional exploit notes, useful commands When to Pivot If you do not yet understand what the binary does, switch to /ctf-reverse before trying to exploit it. If the service is really a restricted shell, encoding puzzle, or sandbox language challenge, switch to /ctf-misc . If the exploit path depends on a web endpoint, session bug, or upload primitive more than memory corruption, switch to /ctf-web . If the vulnerability requires breaking a cryptographic primitive before exploitation, switch to /ctf-crypto . Quick Start Commands # Binary analysis checksec --file=binary file binary readelf -h binary # Find gadgets ROPgadget --binary binary | grep "pop rdi" ropper -f binary --search "pop rdi" one_gadget /lib/x86_64-linux-gnu/libc.so.6 # Debug gdb -q binary -ex 'start' -ex 'checksec' # Pattern for offset finding python3 -c "from pwn import *; print(cyclic(200))" python3 -c "from pwn import *; print(cyclic_find(0x61616168))" # libc identification ./libc-database/find puts <leaked_addr_last_3_nibbles> Source Code Red Flags Threading/ pthread -> race conditions usleep() / sleep() -> timing windows Global variables in multiple threads -> TOCTOU Race Condition Exploitation bash -c '{ echo "cmd1"; echo "cmd2"; sleep 1; } | nc host port' Common Vulnerabilities Buffer overflow: gets() , scanf("%s") , strcpy() Format string: printf(user_input) Integer overflow, UAF, race conditions Protection Implications for Exploit Strategy Protection Status Implication PIE Disabled All addresses (GOT, PLT, functions) are fixed - direct overwrites work RELRO Partial GOT is writable - GOT overwrite attacks possible RELRO Full GOT is read-only - need alternative targets (hooks, vtables, return addr) NX Enabled Can't execute shellcode on stack/heap - use ROP or ret2win Canary Present Stack smash detected - need leak or avoid stack overflow (use heap) Quick decision tree: Partial RELRO + No PIE -> GOT overwrite (easiest, use fixed addresses) Full RELRO -> target __free_hook , __malloc_hook (glibc < 2.34), or return addresses Stack canary present -> prefer heap-based attacks or leak canary first Stack Buffer Overflow Find offset: cyclic 200 then cyclic -l <value> Check protections: checksec --file=binary No PIE + No canary = direct ROP Canary leak via format string or partial overwrite Canary brute-force byte-by-byte on forking servers (7*256 attempts max) ret2win with magic value: Overflow -> ret (alignment) -> pop rdi; ret -> magic -> win(). Stack alignment: SIGSEGV in movaps = add extra ret gadget. Offset: buffer at rbp - N , return at rbp + 8 , total = N + 8. Input filtering: assert payload avoids memmem() banned strings. Gadgets: ROPgadget --binary binary | grep "pop rdi" , or pwntools ROP() for hidden gadgets in CMP immediates. See overflow-basics.md for full exploit code. Parser Stack Overflow (Unchecked memcpy) Pattern: Custom file parser (PCAP, image, archive) allocates fixed stack buffer but input records can exceed it. memcpy copies before length validation, overflowing saved registers and return address. Must restore callee-saved registers: rbx to readable memory (BSS), loop counters to exit values, then ret gadget + win function. See overflow-basics.md . Struct Pointer Overwrite (Heap Menu Challenges) Pattern: Menu create/modify/delete on structs with data buffer + pointer. Overflow name into pointer field with GOT address, then write win address via modify. See overflow-basics.md for full exploit and GOT target selection table. Signed Integer Bypass Pattern: scanf("%d") without sign check; negative quantity * price = negative total, bypasses balance check. See overflow-basics.md . Canary-Aware Partial Overflow Pattern: Overflow valid flag between buffer and canary. Use ./ as no-op path padding for precise length. See overflow-basics.md and advanced.md for full exploit chain. Global Buffer Overflow (CSV Injection) Pattern: Adjacent global variables; overflow via extra CSV delimiters changes filename pointer. See overflow-basics.md and advanced.md for full exploit. ROP Chain Building Leak libc via puts@PLT(puts@GOT) , return to vuln, stage 2 with system("/bin/sh") . See rop-and-shellcode.md for full two-stage ret2libc pattern, leak parsing, and return target selection. DynELF libc discovery: pwntools.DynELF(leak_func, pointer_in_libc) resolves libc symbols remotely without knowing the libc version. See rop-and-shellcode.md . Constrained shellcode in small buffers: When buffer is too small, use read() shellcode stub (< 20 bytes) to pull full stage-2 shellcode. See rop-and-shellcode.md . Raw syscall ROP: When system() / execve() crash (CET/IBT), use pop rax; ret + syscall; ret from libc. See rop-and-shellcode.md . ret2csu: __libc_csu_init gadgets control rdx , rsi , edi and call any GOT function — universal 3-argument call without libc gadgets. See rop-and-shellcode.md . Bad char XOR bypass: XOR payload data with key before writing to .data , then XOR back in place with ROP gadgets. Avoids null bytes, newlines, and other filtered characters. See rop-and-shellcode.md . Exotic gadgets (BEXTR/XLAT/STOSB/PEXT): When standard mov write gadgets are unavailable, chain obscure x86 instructions for byte-by-byte memory writes. See rop-and-shellcode.md . Stack pivot (xchg rax,esp): Swap stack pointer to attacker-controlled heap/buffer when overflow is too small for full ROP chain. Requires pop rax; ret to load pivot address first. See rop-and-shellcode.md . rdx control: After puts() , rdx is clobbered to 1. Use pop rdx; pop rbx; ret from libc, or re-enter binary's read setup + stack pivot. See rop-and-shellcode.md . Canary XOR epilogue as rdx zeroing gadget: When no pop rdx; ret exists, jump into the canary check epilogue xor rdx, fs:28h -- it zeros RDX when the canary is intact. See rop-and-shellcode.md . stub_execveat as execve alternative: When no pop rax; ret exists, use stub_execveat (syscall 322/0x142) instead of execve -- send exactly 0x142 bytes so read() return value sets rax. See rop-and-shellcode.md . Shell interaction: After execve , sleep(1) then sendline(b'cat /flag*') . See rop-and-shellcode.md . Format String Through Input Transformation ROT13-encoded format string: When input is ROT13/Caesar-transformed before reaching printf , pre-encode the format string payload with the inverse transform so it arrives intact. See format-string.md . Kernel Exploitation addr_limit bypass via failed file open: When a kernel module sets addr_limit = KERNEL_DS but fails to restore it on error paths, force the error (e.g., make target file a directory) to retain kernel memory access from userspace read() / write() . See kernel-techniques.md . Sandbox and Emulator Escape