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From: zenith parsec (zenith_parsecthe-astronaut.com)
Date: Sun May 13 2001 - 15:17:22 CDT
Vulnerable systems: redhat 7.0 with man-1.5h1-10 (default
package) and earlier.
Heap Based Overflow of man via -S option gives GID man.
Due to a slight error in a length check, the -S option to
man can cause a buffer overflow on the heap, allowing redirection of execution
into user supplied code.
man -S `perl -e 'print ":" x 100'`
Will cause a seg fault if you are vulnerable.
It is possible to insert a pointer into a linked list that
will allow overwriting of any value in memory that is followed by 4 null
characters (a null pointer). one such
memory location is the last entry on the GOT (global offset table). When another
item is added to the linked list, the address of the data (a filename) is
inserted over the last value, effectively redefining the function
to the code represented by the filename.
Putting shellcode in the filename allows execution of arbitrary code when the
function referred to is called.
Redhat have be contacted, and will be releasing an errata soon.
GID man allows a race condition for root via
/etc/cron.daily/makewhatis and /sbin/makwhatis
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