In this picoCTF 2026 writeup for Echo Escape 1, we walk through a fundamental 64-bit buffer overflow (Ret2Win) exploit. First, we perform binary analysis using checksec and GDB (pwndbg) to identify the lack of stack canaries and PIE. Then, we use a cyclic pattern to calculate the 40-byte offset required to overwrite the return address. Finally, we develop a pwntools Python script to hijack the execution flow and call the hidden 'win' function to capture the flag.
Links & Resources
Challenge: https://play.picoctf.org/practice/cha...
Tools Used: GDB (pwndbg), Pwntools, Python, Checksec
Video Chapters
00:00 Introduction to Echo Escape 1
00:43 Binary Analysis & Security Mitigations (checksec)
01:53 Source Code Walkthrough (Buffer Mismatch)
02:29 Stack Memory & Overflow Theory
04:04 Finding the 'win' Function Address in GDB
04:54 Calculating the Offset with Cyclic Patterns
06:53 Triggering the Segmentation Fault (RIP Overwrite)
08:27 Writing the Pwntools Exploit Script
11:12 Running the Exploit & Flag Capture
11:51 Mitigation Strategies & Outro
#picoctf2026 #bufferoverflow #binaryexploitation #pwn #cybersecurity #ethicalhacking #reverseengineering
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