Apache CGI in user directory "End of script output before headers"

I know there are some questions about this topic, but none seems to solve my issue. See this or this or this.

I'm on Linux, Fedora21, and I'm trying to enable per user directory CGI script. I followed these instructions, but without success.

I get the error:

[cgi:error] End of script output before headers: test.cgi

test.cgi is an executable sh file, containing a very simple script:

#!/usr/bin/sh

echo "Content-type: text/plain"
echo ""
echo "Hello"

which has executable flag and runs without problems from shell. I also tried with Python: same result.

I also disabled selinux for good measure.

I also tried setting the debug level to Apache's ErrorLog, but all I get is only "granted" permissions before the error above.

I also configured the /etc/httpd/conf.d/userdir.conf file with

<Directory "/home/*/public_html">
    AllowOverride All
    Options MultiViews Indexes SymLinksIfOwnerMatch IncludesNoExec
    Require all granted
</Directory>

<Directory /home/*/public_html/cgi-bin/>
    Options ExecCGI FollowSymLinks
    SetHandler cgi-script
    AddHandler cgi-script .cgi .exe .pl .py .vbs
    Require all granted
    AllowOverride All
</Directory>

and restarted the server. No success. Everything looks fine to me, I can't understand... What's wrong??

EDIT:

I forgot to add that the issue is just for per-user directory: if I move the same script to /var/www/cgi-bin directory, it works as expected.

EDIT 2:

The shell does exist:

$ ls /usr/bin/sh
/usr/bin/sh

Solution

Finally I solved that. Thanks to @JimB, because in their comment they pointed out SUEXEC, which I didn't know about (or simply ignored till now).

After reading a bit the suEXEC documentation, I understood the the problem had to be there. So, I took a look at the configuration:

# suexec -V
 -D AP_DOC_ROOT="/var/www"
 -D AP_GID_MIN=1000
 -D AP_HTTPD_USER="apache"
 -D AP_LOG_SYSLOG
 -D AP_SAFE_PATH="/usr/local/bin:/usr/bin:/bin"
 -D AP_UID_MIN=1000
 -D AP_USERDIR_SUFFIX="public_html"

and everything looked Ok (good uid/gid for my user, userdir_suffix is fine, etc). So I took a look at the system logs:

# journalctl -b | grep "suexec"
May 22 11:43:12 caladan suexec[5397]: uid: (1000/user) gid: (1000/user) cmd: test.cgi
May 22 11:43:12 caladan suexec[5397]: directory is writable by others: (/home/user/public_html/cgi-bin)

and that's the problem: my cgi-bin directory was writable by others.

I fixed by simply changing the permissions to 755.