Forwarded from https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1139275

A certain poison pill message seems to crash sieve-filter. A reproducer script, email message, and sieve script are at https://salsa.debian.org/noahm/dovecot/-/tree/sieve-crash/debian/tests/sieve...

The problem is not reproducible with 2.4.1, so it seems to be a regression introduced since then.

Coredump details follow:

root@dovecot-test:/home/noahm/dovecot# coredumpctl info | cat PID: 110911 (sieve-filter) TID: 110911 (sieve-filter) UID: 65534 (nobody) GID: 65534 (nogroup) Signal: 6 (ABRT) Timestamp: Mon 2026-06-08 19:16:37 UTC (29s ago) Command Line: sieve-filter -u dep8 -e -W -D -C -v /srv/dovecot-dep8/test.sieve INBOX Executable: /usr/bin/sieve-filter Control Group: /user.slice/user-1000.slice/session-5.scope Unit: session-5.scope Slice: user-1000.slice Session: 5 Owner UID: 1000 (noahm) Boot ID: 46469969e01043559d913ef8ab625856 Machine ID: a497a098bd094c1c8f7c8ed02aa21853 Hostname: dovecot-test Storage: /var/lib/systemd/coredump/core.sieve-filter.65534.46469969e01043559d913ef8ab625856.110911.1780946197000000.zst (present) Size on Disk: 253.5K Message: Process 110911 (sieve-filter) of user 65534 dumped core. Module libgcc_s.so.1 from deb gcc-16-16.1.0-1.amd64 Module libstdc++.so.6 from deb gcc-16-16.1.0-1.amd64 Stack trace of thread 110911: #0 0x00007fe06b09fcfc n/a (libc.so.6 + 0x97cfc) #1 0x00007fe06b048d02 raise (libc.so.6 + 0x40d02) #2 0x00007fe06b0304b2 abort (libc.so.6 + 0x284b2) #3 0x00007fe06b26ed45 n/a (libdovecot.so.0 + 0x6ed45) #4 0x00007fe06b357597 default_fatal_handler (libdovecot.so.0 + 0x157597) #5 0x00007fe06b26ec72 i_panic (libdovecot.so.0 + 0x6ec72) #6 0x00007fe06b273b90 n/a (libdovecot.so.0 + 0x73b90) #7 0x00007fe06b3498fb n/a (libdovecot.so.0 + 0x1498fb) #8 0x00007fe06b34a784 n/a (libdovecot.so.0 + 0x14a784) #9 0x00007fe06b34a93b buffer_append (libdovecot.so.0 + 0x14a93b) #10 0x00007fe06b344cc6 dregex_code_match_groups (libdovecot.so.0 + 0x144cc6) #11 0x00007fe06b806a27 n/a (libdovecot-sieve.so.0 + 0x6da27) #12 0x00007fe06b806cd0 n/a (libdovecot-sieve.so.0 + 0x6dcd0) #13 0x00007fe06b7ee411 sieve_match_value (libdovecot-sieve.so.0 + 0x55411) #14 0x00007fe06b7ee711 sieve_match (libdovecot-sieve.so.0 + 0x55711) #15 0x00007fe06b7f5862 n/a (libdovecot-sieve.so.0 + 0x5c862) #16 0x00007fe06b7eccde sieve_interpreter_continue (libdovecot-sieve.so.0 + 0x53cde) #17 0x00007fe06b7fbfbe sieve_execute (libdovecot-sieve.so.0 + 0x62fbe) #18 0x00005638c0022fcf main (sieve-filter + 0x3fcf) #19 0x00007fe06b031f77 n/a (libc.so.6 + 0x29f77) #20 0x00007fe06b032027 __libc_start_main (libc.so.6 + 0x2a027) #21 0x00005638c0023791 _start (sieve-filter + 0x4791) ELF object binary architecture: AMD x86-64