I have this problem on my Ubuntu Server:
Problem
Some time my sites are not reachable from the browser and I can see a "Time Out Error", however the server replies to PING requests. I checked the error.log file ~ 50MB of data similar to the following (in some hours of downtime).
In order to fix this error I have to reboot apache with the command service apache2 restart
[...]
*** stack smashing detected ***: <unknown> terminated
*** stack smashing detected ***: <unknown> terminated
*** stack smashing detected ***: <unknown> terminated
*** stack smashing detected ***: <unknown> terminated
[Sat Mar 09 14:33:05.391789 2019] [core:notice] [pid 5157] AH00051: child pid 9724 exit signal Segmentation fault (11), possible coredump in /etc/apache2
[Sat Mar 09 14:33:05.391807 2019] [core:error] [pid 5157] AH00546: no record of generation 0 of exiting child 9724
[Sat Mar 09 14:33:05.391818 2019] [core:notice] [pid 5157] AH00051: child pid 9726 exit signal Segmentation fault (11), possible coredump in /etc/apache2
[Sat Mar 09 14:33:05.391821 2019] [core:error] [pid 5157] AH00546: no record of generation 0 of exiting child 9726
[Sat Mar 09 14:33:05.391835 2019] [core:notice] [pid 5157] AH00051: child pid 9728 exit signal Segmentation fault (11), possible coredump in /etc/apache2
[Sat Mar 09 14:33:05.391837 2019] [core:error] [pid 5157] AH00546: no record of generation 0 of exiting child 9728
Software
Ubuntu 18.10
Server version: Apache/2.4.34 (Ubuntu)
Server built: 2018-10-03T13:57:22
PHP 7.2.15-0ubuntu0.18.10.1 (cli) (built: Feb 8 2019 14:54:22) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies
with Zend OPcache v7.2.15-0ubuntu0.18.10.1, Copyright (c) 1999-2018, by Zend Technologies
Hardware
/W path Device Class Description
======================================================
system MS-7B46 (Default string)
/0 bus Z370 SLI PLUS (MS-7B46)
/0/0 memory 64KiB BIOS
/0/3c memory 8GiB System Memory
/0/3c/0 memory [empty]
/0/3c/1 memory 8GiB DIMM DDR4 Synchronous Unbuffered (Unregistered) 2667 MHz (0,4 ns)
/0/3c/2 memory [empty]
/0/3c/3 memory [empty]
/0/42 memory 384KiB L1 cache
/0/43 memory 1536KiB L2 cache
/0/44 memory 9MiB L3 cache
/0/45 processor Intel(R) Core(TM) i5-8600K CPU @ 3.60GHz
/0/100 bridge 8th Gen Core Processor Host Bridge/DRAM Registers
/0/100/8 generic Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th Gen Core Processor Gaussian Mixture Model
/0/100/14 bus 200 Series/Z370 Chipset Family USB 3.0 xHCI Controller
/0/100/14/0 usb1 bus xHCI Host Controller
/0/100/14/0/9 bus USB2.0 Hub
/0/100/14/0/9/2 input USB Receiver
/0/100/14/0/9/3 input Wireless Receiver
/0/100/14/0/9/4 input Wired Keyboard 600
/0/100/14/0/a storage USB FLASH DRIVE
/0/100/14/1 usb2 bus xHCI Host Controller
/0/100/14.2 generic 200 Series PCH Thermal Subsystem
/0/100/16 communication 200 Series PCH CSME HECI #1
/0/100/17 storage 200 Series PCH SATA controller [AHCI mode]
/0/100/1c bridge 200 Series PCH PCI Express Root Port #1
/0/100/1c.2 bridge 200 Series PCH PCI Express Root Port #3
/0/100/1c.2/0 display GP107 [GeForce GTX 1050]
/0/100/1c.2/0.1 multimedia GP107GL High Definition Audio Controller
/0/100/1c.4 bridge 200 Series PCH PCI Express Root Port #5
/0/100/1c.4/0 bus ASMedia Technology Inc.
/0/100/1c.4/0/0 usb3 bus xHCI Host Controller
/0/100/1c.4/0/1 usb4 bus xHCI Host Controller
/0/100/1f bridge Z370 Chipset LPC/eSPI Controller
/0/100/1f.2 memory Memory controller
/0/100/1f.3 multimedia 200 Series PCH HD Audio
/0/100/1f.4 bus 200 Series/Z370 Chipset Family SMBus Controller
/0/100/1f.6 enp0s31f6 network Ethernet Connection (2) I219-V
/0/1 scsi5 storage
/0/1/0.0.0 /dev/sda disk 240GB DREVO X1 SSD
/0/1/0.0.0/1 /dev/sda1 volume 498MiB Windows NTFS volume
/0/1/0.0.0/2 /dev/sda2 volume 99MiB Windows FAT volume
/0/1/0.0.0/3 /dev/sda3 volume 15MiB System partition
/0/1/0.0.0/4 /dev/sda4 volume 112GiB Windows NTFS volume
/0/1/0.0.0/5 /dev/sda5 volume 43GiB EXT4 volume
/0/1/0.0.0/6 /dev/sda6 volume 1258MiB Linux swap volume
/0/1/0.0.0/7 /dev/sda7 volume 24GiB EXT4 volume
/0/1/0.0.0/8 /dev/sda8 volume 40GiB EXT4 volume
/0/2 scsi6 storage
/0/2/0.0.0 /dev/sdb disk 31GB USB FLASH DRIVE
/0/2/0.0.0/0 /dev/sdb disk 31GB
/0/2/0.0.0/0/1 /dev/sdb1 volume 28GiB Windows FAT volume
/1 power To Be Filled By O.E.M.
