Re: [exim/exim] [Bug]: A userforward which saves to a file and then delivers fails to set uid under heavy load (Issue #3235)

The flowing script may be used to reproduce this situation:

#!/bin/sh

COUNT=100
MAILTO="[email protected])"

i=1
while [ ${i} -le ${COUNT} ]
do
       echo TEST | mail -s "Cron test #"${i} ${MAILTO}
       i=`expr ${i} + 1`
done

Some messages is delivered immidiatly and another puts on queue. Runing exiqgrep -f . -i | xargs exim -M trigers the above error:

2026-08-03 12:46:41 1wqpF8-00000000HOs-0sQZ unable to set gid=0 or uid=1001 (euid=26): userforward router (recipient is [email protected])
2026-08-03 12:46:41 1wqpF8-00000000HOs-0sQZ internal problem in userforward router (recipient is [email protected]): failure to transfer data from subprocess: status=0100 readerror='No such file or directory'
2026-08-03 12:46:41 1wqpF8-00000000HOs-0sQZ == [email protected] R=userforward defer (-1): internal problem in userforward router (recipient is [email protected]): failure to transfer data from subprocess: status=0100 readerror='No such file or directory'

Then all messages is delivered to both local mailbox and remote host. Exim binary is running with suid bit and deliver_drop_privilege is unset.

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View it on Exim Forgejo ( https://code.exim.org/exim/exim/issues/3235#issuecomment-239962 ) or reply to this email directly.