Hi Michael,
Has anyone ever seen this before? Can anyone maybe confirm this on his own host with Debian 11 and Apache 2.4.51?
Yes, I've seen this before when I tried to set up a Koha 21.05 instance for testing purposes on a Debian 11 VM. I can confirm it is still happening with Koha 21.11.00 on Debian 11.1.0 with Apache 2.4.51-1~deb11u1 and Plack enabled (mod_itk enabled too which is on version 2.4.7-04-1+b1). Sometimes the segmentation faults arrive "in batches" like the 5 entries in the log file below: ==> /var/log/apache2/error.log <== [Fri Dec 10 11:14:02.082457 2021] [core:notice] [pid 1915] AH00052: child pid 2108 exit signal Segmentation fault (11) [Fri Dec 10 11:14:02.082696 2021] [core:notice] [pid 1915] AH00052: child pid 2116 exit signal Segmentation fault (11) [Fri Dec 10 11:14:02.082733 2021] [core:notice] [pid 1915] AH00052: child pid 2120 exit signal Segmentation fault (11) [Fri Dec 10 11:14:02.082760 2021] [core:notice] [pid 1915] AH00052: child pid 2124 exit signal Segmentation fault (11) [Fri Dec 10 11:14:02.082786 2021] [core:notice] [pid 1915] AH00052: child pid 2128 exit signal Segmentation fault (11) The following report from the Debian bug tracking system seems to be referring to similar findings: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=995961 The earliest report of this issue seems to be from Gentoo's Bugzilla: https://bugs.gentoo.org/816258 And here's the entry filed upstream (currently in Status "NEW"): https://bz.apache.org/bugzilla/show_bug.cgi?id=65627 HTH, Andreas