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From: houjingyi <houjingyi647 AT gmail DOT com>
Date: Tue, 5 Nov 2019 17:45:14 +0800
Message-ID: <CAN1eSkv02aZZb-09sYYwidexjZBNsPcMsEuit95P12r6vkccZw@mail.gmail.com>
Subject: report security problem
To: cygwin AT cygwin DOT com
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fhandler_console::create_invisible_console_workaround in
newlib-cygwin\winsup\cygwin\fhandler_console.cc will call CreateProcessW to
create a new hidden process. According to CreateProcessW documention:

The lpApplicationName parameter can be NULL. In that case, the module name
must be the first white space–delimited token in the lpCommandLine string.
If you are using a long file name that contains a space, use quoted strings
to indicate where the file name ends and the arguments begin; otherwise,
the file name is ambiguous. For example, consider the string "c:\program
files\sub dir\program name". This string can be interpreted in a number of
ways. The system tries to interpret the possibilities in the following
order:
c:\program.exe
c:\program files\sub.exe
c:\program files\sub dir\program.exe
c:\program files\sub dir\program name.exe

Unfortunately fhandler_console::create_invisible_console_workaround did not
use quote. This problem can be triggered by many ways since
the component was used by other softwares. I can confirm it can at least be
triggered by git(https://git-scm.com/download/win). Just create program.exe
and put it to C:\problem.exe, git-bash.exe creates process mintty.exe,
mintty.exe loads msys-2.0.dll which contains the vulnerable code and
program.exe get executed(I will inform git too).

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