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Potential Denial of Service Vulnerability in embedded commands - Bash ve

From: Alex Nichols
Subject: Potential Denial of Service Vulnerability in embedded commands - Bash version 4.4.12(1) - Release
Date: Tue, 7 Nov 2017 11:58:40 +0000

Hi All,

I’m an Ethical Hacking student at Coventry university and while doing some
exploit development on my Linux boxes I stumbled across a bug in the bash
4.4.12(1) - release.

In order to trigger the bug I executed the command *`*cat sploit.buf*`*
where sploit.buf is a just over 2GB file of ‘A’ characters. When this
command is executed the bash terminal crashes with the following error
“Bash: xrealloc: .././subst.c:5977: cannot allocate 1073741824 bytes
(2149011456 bytes allocated)”, on Ubuntu 17.10 64 bit. This error message
appears to vary on different Linux distros. On Kali 2017.2 64 bit the error
message is ” Bash: xrealloc: .././subst.c:5977: cannot allocate
18446744071562067968 bytes (4296613888 bytes allocated)”.

This bug may present a potential security risk as a malicious user may be
able to crash a users bash session by tricking them into executing a
malicious bash script.

I will be adhering to the ICS-CERT Vulnerability Disclosure Policy and look
forward to further discussing and resolving this bug



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