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AutoDesk Meshmixer macOS Installer Local Privilege Escalation

Medium

Synopsis

In the installation package for AutoDesk Meshmixer for macOS prior to December 22, 2021, the "postinstall" script included in the installer allows for local privilege escalation to root privileges due to improper permissions on files used throughout the installation process.

During the installation process for Meshmixer, the following postinstall script is run as root: 

#!/bin/sh
set -e
srcPath=/tmp/Autodesk
destPath=~/Documents
if [ ! -e "$srcPath" ]; then
 echo "$srcPath: No such file or directory"
 exit
fi
mkdir -p "$destPath/meshmixer"
cp -R "$srcPath/meshmixer2.3/"* "$destPath/meshmixer"
if [ -e ~/Documents/meshmixer/libraries/default ]; then
 find ~/Documents/meshmixer/libraries/default -type f -name *.prt -maxdepth 1 -exec cp -n {} ~/Documents/meshmixer/libraries/parts/user/My\ Parts/ \;
 find ~/Documents/meshmixer/libraries/default -type f -name *.png -maxdepth 1 -exec cp -n {} ~/Documents/meshmixer/libraries/parts/user/My\ Parts/ \;
 find ~/Documents/meshmixer/libraries/default -type f -name *.obj -maxdepth 1 -exec cp -n {} ~/Documents/meshmixer/libraries/parts/user/My\ Parts/ \;
fi
chmod -R 777 "$destPath/meshmixer"
exit 0

 

By placing a malicious symlink in "/tmp/Autodesk/meshmixer2.3", an attacker could cause files normal accessible by only the root user to be copied to "~/Documents/meshmixer" and have the permissions changed to "777", which allows the file(s) to be read by anyone.

Further, if a meshmixer install does not exist prior to installation, the user could create their own malicious file and place it in "/tmp/Autodesk/meshmixer2.3" and create a symlink for "~/Documents/meshmixer" that would cause their custom file to be place anywhere on the system (such as /Library/LaunchDaemons, which could spawn an application of their choosing as the root user), which results in privilege escalation to root with the possibility of code execution.

Solution

Use latest available installer.

Disclosure Timeline

August 10, 2021 - Tenable disclosed via AutoDesk security webform.
August 19, 2021 - Tenable makes second disclosure attempt.
August 23, 2021 - Vendor directs Tenable to HackerOne bounty program. Tenable states that we are unable to submit through that avenue and requests a separate contact.
September 10, 2021 - Vendor directs Tenable to HackerOne bounty program. Tenable states that we are unable to submit through that avenue and requests a separate contact.
September 14, 2021 - Tenable requests permission to submit to PSIRT Autodesk directly.
September 27, 2021 - Tenable submits to PSIRT Autodesk directly.
November 19, 2021 - Vendor requests details on policy conflict.
November 22, 2021 - Tenable provides details.
December 22, 2021 - Vendor states that a fix has been made available.

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Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

Risk Information

Tenable Advisory ID: TRA-2021-53
Credit:
Jimi Sebree
Affected Products:
Autodesk Meshmixer macOS Installers prior to Dec. 22, 2021
Risk Factor:
Medium

Advisory Timeline

December 30, 2021 - Initial release.