I got the same issue on the latest update just now on a RPi 3B+
output from gdb:
Attaching to process 15834
[New LWP 15835]
[New LWP 15836]
[New LWP 15837]
[New LWP 15838]
[New LWP 15839]
[New LWP 15840]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/arm-linux-gnueabihf/libthread_db.so.1".
__GI___poll (timeout=-1, nfds=6, fds=0xede7b0) at ../sysdeps/unix/sysv/linux/poll.c:29
29 ../sysdeps/unix/sysv/linux/poll.c: No such file or directory.
(gdb) continue
Continuing.
[New Thread 0x735ff460 (LWP 15849)]
[Thread 0x735ff460 (LWP 15849) exited]
[New Thread 0x735ff460 (LWP 15850)]
[Detaching after fork from child process 15851]
[Thread 0x735ff460 (LWP 15850) exited]
[New Thread 0x735ff460 (LWP 15852)]
Thread 5 "database" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x74f3f460 (LWP 15838)]
__strchrnul (s=0x1 <error: Cannot access memory at address 0x1>, c_in=37) at strchrnul.c:50
50 strchrnul.c: No such file or directory.
(gdb) backtrace
#0 __strchrnul (s=0x1 <error: Cannot access memory at address 0x1>, c_in=37) at strchrnul.c:50
#1 0x76d5c174 in __find_specmb (format=0x1 <error: Cannot access memory at address 0x1>) at printf-parse.h:108
#2 _IO_vfprintf_internal (s=s@entry=0x74f3eac0, format=format@entry=0x1 <error: Cannot access memory at address 0x1>, ap=..., ap@entry=...) at vfprintf.c:1315
#3 0x76e04024 in __GI___vasprintf_chk (result_ptr=result_ptr@entry=0x74f3ec60, flags=flags@entry=1, format=0x1 <error: Cannot access memory at address 0x1>, format@entry=0x0, args=...,
args@entry=...) at vasprintf_chk.c:66
#4 0x76e03f30 in __asprintf_chk (result_ptr=result_ptr@entry=0x74f3ec60, flags=flags@entry=1, format=0x1 <error: Cannot access memory at address 0x1>) at asprintf_chk.c:32
#5 0x00484b2a in asprintf (__fmt=0x56f5d4 "SELECT id FROM network WHERE hwaddr = '%s';", __ptr=0x74f3ec60) at /usr/arm-linux-gnueabihf/include/bits/stdio2.h:178
#6 parse_neighbor_cache () at src/database/network-table.c:382
#7 0x00487ae0 in DB_thread (val=<optimized out>) at src/database/database-thread.c:68
#8 0x76e6f494 in start_thread (arg=0x74f3f460) at pthread_create.c:486
#9 0x76df2578 in ?? () at ../sysdeps/unix/sysv/linux/arm/clone.S:73 from /lib/arm-linux-gnueabihf/libc.so.6
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) continue
Continuing.
Thread 5 "database" received signal SIGABRT, Aborted.
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
50 ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) backtrace
#0 __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
#1 0x76d32230 in __GI_abort () at abort.c:79
#2 0x0048cb9c in SIGSEGV_handler (sig=<optimized out>, si=<optimized out>, unused=<optimized out>) at src/signals.c:80
#3 <signal handler called>
#4 __strchrnul (s=0x1 <error: Cannot access memory at address 0x1>, c_in=37) at strchrnul.c:50
#5 0x76d5c174 in __find_specmb (format=0x1 <error: Cannot access memory at address 0x1>) at printf-parse.h:108
#6 _IO_vfprintf_internal (s=s@entry=0x74f3eac0, format=format@entry=0x1 <error: Cannot access memory at address 0x1>, ap=..., ap@entry=...) at vfprintf.c:1315
#7 0x76e04024 in __GI___vasprintf_chk (result_ptr=result_ptr@entry=0x74f3ec60, flags=flags@entry=1, format=0x1 <error: Cannot access memory at address 0x1>, format@entry=0x0, args=...,
args@entry=...) at vasprintf_chk.c:66
#8 0x76e03f30 in __asprintf_chk (result_ptr=result_ptr@entry=0x74f3ec60, flags=flags@entry=1, format=0x1 <error: Cannot access memory at address 0x1>) at asprintf_chk.c:32
#9 0x00484b2a in asprintf (__fmt=0x56f5d4 "SELECT id FROM network WHERE hwaddr = '%s';", __ptr=0x74f3ec60) at /usr/arm-linux-gnueabihf/include/bits/stdio2.h:178
#10 parse_neighbor_cache () at src/database/network-table.c:382
#11 0x00487ae0 in DB_thread (val=<optimized out>) at src/database/database-thread.c:68
#12 0x76e6f494 in start_thread (arg=0x74f3f460) at pthread_create.c:486
#13 0x76df2578 in ?? () at ../sysdeps/unix/sysv/linux/arm/clone.S:73 from /lib/arm-linux-gnueabihf/libc.so.6
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
gdb) continue
Continuing.
Unable to fetch general registers.: No such process.
Unable to fetch general registers.: No such process.
(gdb) [Thread 0x735ff460 (LWP 15852) exited]
[Thread 0x73f3d460 (LWP 15840) exited]
[Thread 0x7473e460 (LWP 15839) exited]
[Thread 0x75740460 (LWP 15837) exited]
[Thread 0x75f41460 (LWP 15836) exited]
[Thread 0x76742460 (LWP 15835) exited]
[Thread 0x76d19010 (LWP 15834) exited]
Program terminated with signal SIGABRT, Aborted.
The program no longer exists.
# pihole -v
Pi-hole version is v4.3.5-455-gfff7adf (Latest: v4.4)
AdminLTE version is v4.3.2-457-g0a81dadf (Latest: v4.3.3)
FTL version is vDev-81c4eac (Latest: v4.3.1)