Fedora has issued an advisory on June 19:
The issue is fixed upstream in 1.12.0.
Assigning to wally as both registered and actual maintainer.
Fixed upstream in 1.12.0
Added an upstream patch  to fix the issue. Please test mutt-1.11.4-1.1.mga7 from core/updates_testing.
Updated mutt packages fix security vulnerability:
Invalid format of RFC parameter passed to atoi() function in rfc2231.c could
lead to unexpected behavior (rhbz#1710397, bdo#929017).
MGA7-64 Plasma on Lenovo B50
No installation issues.
Found some info on the use of mutt at https://www.thegeekdiary.com/how-to-install-and-configure-mutt-in-centos-rhel/
Tried to use mutt to send an e-mail from my hotmail account to my gmail account, but got into trouble defining the smtp parameters
MS seems to do something strange for "direct mail"
Swapped around, sending from gmail to hotmail gets me a bt further but still I run into a problem I cannot solve right now:
$ echo "" | mutt -s "testmutt" -i body.txt email@example.com
Verbinding met smtp.gmail.com beëindigd (Connection closed)
SMTP-sessie is mislukt: leesfout (smptp session failed: read error)
Bericht kon niet verstuurd worden. (message could not be sent)
The file body.txt used in the command just contains one line of plain text.
Sending this on the basis of a clean install.
Validating. Advisory in Comment 4.
In case you're interested... one way you can do some amount of testing with mutt is to open any mailbox (look in /var/spool/mail) on your system that has something in it. Mine has...
$ ll /var/spool/mail
-rw------- 1 apache mail 2304 Nov 2 2016 apache
-rw------- 1 mrambo mail 1459 May 17 2019 mrambo
-rw------- 1 postfix mail 2164679 Feb 14 04:02 postfix
All three of those boxes contain something (the size will be 0 if it does not). You can read them with mutt.
sudo mutt -f /var/spool/mail postfix
You won't need sudo or have to become root if you own the mailbox you're opening. Once mutt opens you should be able to manipulate the mails in about any way short of replying to them since you probably won't have smtp set up yet. Anyway, this will at least enable you to see mutt do something with some mail.
Opps - that should be sudo mutt -f /var/spool/mail/postfix
An update for this issue has been pushed to the Mageia Updates repository.