#612·upx

UPX compressed arm64/amd64/x86_64 executable crashes on macOS Ventura 13.0

Author: chchwyCreated Oct 25, 2022Updated Jun 18, 2026

Labelsenhancementhelp wantedos:macOS

This issue tracker is ONLY used for reporting bugs. Please use stackoverflow for supporting issues.

What's the problem (or question)?

The UPX compressed amd64 executable crashes on macOS 13.0. I made a small CMake project which merely print out a few lines of text for reproducing the crash.

Here are the commands I used to compress the executable. Then it crashed immediately after I ran the compressed one.

bash

% upx -vk ./HelloUPX4 -o./HelloUPX4-compressed
Ultimate Packer for eXecutables
                          Copyright (C) 1996 - 2020
UPX 3.96        Markus Oberhumer, Laszlo Molnar & John Reiser   Jan 23rd 2020

        File size         Ratio      Format      Name
   --------------------   ------   -----------   -----------
     82304 ->     12304   14.95%   macho/amd64   HelloUPX4-compressed          

Packed 1 file.

% ./HelloUPX4-compressed 
zsh: segmentation fault  ./HelloUPX4-compressed
%

lldb

bash

% lldb ./HelloUPX4-compressed 
(lldb) target create "./HelloUPX4-compressed"
Current executable set to '/Users/matt/HelloUPX4/build/Debug/HelloUPX4-compressed' (x86_64).
(lldb) run
Process 14499 launched: '/Users/matt/HelloUPX4/build/Debug/HelloUPX4-compressed' (x86_64)
Process 14499 stopped
* thread #1, stop reason = EXC_BAD_ACCESS (code=1, address=0x21090c000)
    frame #0: 0x000000021090c000
error: memory read failed for 0x21090c000
Target 0: (HelloUPX4-compressed) stopped.
(lldb) exit

What should have happened?

It should print the same text as before it was compressed.

This is the output when it is not compressed.

% lldb "HelloUPX4"
(lldb) target create "HelloUPX4"
Current executable set to '/Users/evatu/Work/HelloUPX4/build/Debug/HelloUPX4' (x86_64).
(lldb) run
Process 14516 launched: '/Users/evatu/Work/HelloUPX4/build/Debug/HelloUPX4' (x86_64)
Hello UPX4!
Done.
Process 14516 exited with status = 0 (0x00000000)

Do you have an idea for a solution?

Actually no, but It was working on macOS 12.

How can we reproduce the issue?

I made a tiny CMake project with 16 lines of code for this bug report. It is configured to generate an amd64 executable. (Not arm64)

Clone the project at https://github.com/chchwy/upx-macos13-crash and go to the folder
mkdir build
cd build
cmake .. -G Xcode
cmake --build .
upx -vk ./Debug/HelloUPX4 -o./Debug/HelloUPX4-compressed
./Debug/HelloUPX4-compressed <= crashed here

Please tell us details about your environment.

UPX version used (upx --version): 3.96 (I tried the latest devel4 branch and it doesn't work either)
Host Operating System and version: macOS 13.0 Ventura
Host CPU architecture: arm64
Target Operating System and version: same
Target CPU architecture: amd64 (or called x86_64)

Source: upx/upx

View original on GitHub View discussion on GitHub