picoCTF Solutions
picoGym ExclusiveReverse EngineeringMedium

Bit-O-Asm-2

Published: March 5, 2024Updated: December 9, 2025

Description

Follow the memory references in the second disassembly dump to recover the value moved into EAX, then convert it from hexadecimal to decimal.

Setup

Assembly readingDownload disassembler-dump0_b.txt

Fetch the dump and inspect the MOV that assigns DWORD PTR [rbp-0x4] to EAX.

wget https://artifacts.picoctf.net/c/510/disassembler-dump0_b.txt
cat disassembler-dump0_b.txt

Solution

  1. Step 1Resolve the stored constant
    The dump shows 0x9fe1a being written to [rbp-0x4], and that value is later moved into EAX.
  2. Step 2Convert 0x9fe1a to decimal
    Translate 0x9fe1a into decimal (654874) using printf or python, then format the flag as picoCTF{654874}.
    printf "picoCTF{%d}\n" 0x9fe1a

Flag

picoCTF{654874}

Each Bit-O-Asm stage reinforces reading registers and stack slots straight from the disassembly.