Unix Shell Redirection Race Condition Vulnerability

bash, tcsh, cash, ksh and sh are all variations of the Unix shell distributed with many Unix and Unix clone operating systems. A vulnerability exists in these shells that could allow an attacker to arbitrarily write to files.

A vulnerability has been discovered in a number of Unix shells which may allow a local attacker to corrupt files or potentially elevate privileges.

Scripts and command line operations using << as a redirection operator create files in the /tmp directory with a predictable naming convention. Additionally, files are created in the /tmp directory without first checking if the file already exists.

This could result in a symbolic link attack that could be used to corrupt any file that the owner of the redirecting shell has access to write to. This issue affects those systems running vulnerable versions of bash, tcsh, cash, ksh and sh.

ksh is reportedly not vulnerable for IBM AIX systems.


 

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