Program: CWE-78
Project: CVE-2021-32749
Buggy source:
# Fail2Ban configuration file
#
# Author: Cyril Jaquier
#
#

[Definition]

# Option:  actionstart
# Notes.:  command executed once at the start of Fail2Ban.
# Values:  CMD
#
actionstart = printf %%b "Hi,\n
              The jail <name> has been started successfully.\n
              Output will be buffered until <lines> lines are available.\n
              Regards,\n
              Fail2Ban"|mail -s "[Fail2Ban] <name>: started on `uname -n`" <dest>

# Option:  actionstop
# Notes.:  command executed once at the end of Fail2Ban
# Values:  CMD
#
actionstop = if [ -f <tmpfile> ]; then
                 printf %%b "Hi,\n
                 These hosts have been banned by Fail2Ban.\n
                 `cat <tmpfile>`
                 Regards,\n
                 Fail2Ban"|mail -s "[Fail2Ban] <name>: Summary from `uname -n`" <dest>
                 rm <tmpfile>
             fi
             printf %%b "Hi,\n
             The jail <name> has been stopped.\n
             Regards,\n
             Fail2Ban"|mail -s "[Fail2Ban] <name>: stopped on `uname -n`" <dest>

# Option:  actioncheck
# Notes.:  command executed once before each actionban command
# Values:  CMD
#
actioncheck = 

# Option:  actionban
# Notes.:  command executed when banning an IP. Take care that the
#          command is executed with Fail2Ban user rights.
# Tags:    See jail.conf(5) man page
# Values:  CMD
#
actionban = printf %%b "`date`: <ip> (<failures> failures)\n" >> <tmpfile>
            LINE=$( wc -l <tmpfile> | awk '{ print $1 }' )
            if [ $LINE -ge <lines> ]; then
                printf %%b "Hi,\n
                These hosts have been banned by Fail2Ban.\n
                `cat <tmpfile>`
                \nRegards,\n
                Fail2Ban"|mail -s "[Fail2Ban] <name>: Summary" <dest>
                rm <tmpfile>
            fi

# Option:  actionunban
# Notes.:  command executed when unbanning an IP. Take care that the
#          command is executed with Fail2Ban user rights.
# Tags:    See jail.conf(5) man page
# Values:  CMD
#
actionunban = 

[Init]

# Default name of the chain
#
name = default

# Default number of lines that are buffered
#
lines = 5

# Default temporary file
#
tmpfile = /var/run/fail2ban/tmp-mail.txt

# Destination/Addressee of the mail
#
dest = root


Fixed version (ground truth):
# Fail2Ban configuration file
#
# Author: Cyril Jaquier
#
#

[Definition]

# Option:  actionstart
# Notes.:  command executed once at the start of Fail2Ban.
# Values:  CMD
#
actionstart = printf %%b "Hi,\n
              The jail <name> has been started successfully.\n
              Output will be buffered until <lines> lines are available.\n
              Regards,\n
              Fail2Ban"|mail -E 'set escape' -s "[Fail2Ban] <name>: started on `uname -n`" <dest>

# Option:  actionstop
# Notes.:  command executed once at the end of Fail2Ban
# Values:  CMD
#
actionstop = if [ -f <tmpfile> ]; then
                 printf %%b "Hi,\n
                 These hosts have been banned by Fail2Ban.\n
                 `cat <tmpfile>`
                 Regards,\n
                 Fail2Ban"|mail -E 'set escape' -s "[Fail2Ban] <name>: Summary from `uname -n`" <dest>
                 rm <tmpfile>
             fi
             printf %%b "Hi,\n
             The jail <name> has been stopped.\n
             Regards,\n
             Fail2Ban"|mail -E 'set escape' -s "[Fail2Ban] <name>: stopped on `uname -n`" <dest>

# Option:  actioncheck
# Notes.:  command executed once before each actionban command
# Values:  CMD
#
actioncheck = 

# Option:  actionban
# Notes.:  command executed when banning an IP. Take care that the
#          command is executed with Fail2Ban user rights.
# Tags:    See jail.conf(5) man page
# Values:  CMD
#
actionban = printf %%b "`date`: <ip> (<failures> failures)\n" >> <tmpfile>
            LINE=$( wc -l <tmpfile> | awk '{ print $1 }' )
            if [ $LINE -ge <lines> ]; then
                printf %%b "Hi,\n
                These hosts have been banned by Fail2Ban.\n
                `cat <tmpfile>`
                \nRegards,\n
                Fail2Ban"|mail -E 'set escape' -s "[Fail2Ban] <name>: Summary" <dest>
                rm <tmpfile>
            fi

# Option:  actionunban
# Notes.:  command executed when unbanning an IP. Take care that the
#          command is executed with Fail2Ban user rights.
# Tags:    See jail.conf(5) man page
# Values:  CMD
#
actionunban = 

[Init]

# Default name of the chain
#
name = default

# Default number of lines that are buffered
#
lines = 5

# Default temporary file
#
tmpfile = /var/run/fail2ban/tmp-mail.txt

# Destination/Addressee of the mail
#
dest = root