Package: dovecot-imapd Version: 1:2.4.1+dfsg1-6+deb13u6 Severity: normal I was experimenting with using Vivaldi Mail, and dovecot-imapd started crashing repeatedly when Vivaldi was trying to sync and index my (huge) mailbox.
Messages logged by Dovecot: 2026-08-14 10:26:43 imap(ian)<466672><Dy4ka/5Y9r1SRXa8>: Panic: file istream-header-filter.c: line 665 (i_stream_header_filter_snapshot_free): assertion failed: (snapshot->mstream->snapshot_pending) 2026-08-14 10:26:43 imap(ian)<466672><Dy4ka/5Y9r1SRXa8>: Error: Raw backtrace: #1 [unw_get_proc_name() failed: -10] -> #2 [unw_get_proc_name() failed: -10] -> #3 i_panic[0x7fe47ca655e6] -> #4 [unw_get_proc_name() failed: -10] -> #5 i_stream_snapshot_free[0x7fe47cb45c00] -> #6 i_stream_unref[0x7fe47cb45c70] -> #7 [unw_get_proc_name() failed: -10] -> #8 [unw_get_proc_name() failed: -10] -> #9 index_mail_get_special[0x7fe47cd494c0] -> #10 mail_get_special[0x7fe47ccc2700] -> #11 [unw_get_proc_name() failed: -10] -> #12 [unw_get_proc_name() failed: -10] -> #13 imap_fetch_more[0x561b58c5cf80] -> #14 cmd_fetch[0x561b58c50e40] -> #15 command_exec[0x561b58c5a080] -> #16 [unw_get_proc_name() failed: -10] -> #17 [unw_get_proc_name() failed: -10] -> #18 [unw_get_proc_name() failed: -10] -> #19 client_handle_input[0x561b58c60990] -> #20 client_input[0x561b58c60ed0] -> #21 io_loop_call_io[0x7fe47cb51750] -> #22 io_loop_handler_run_internal[0x7fe47cb534f0] -> #23 io_loop_handler_run[0x7fe47cb53680] -> #24 io_loop_run[0x7fe47cb53860] -> #25 master_service_run[0x7fe47caa6330] -> #26 main[0x561b58c4b880] -> #27 [unw_get_proc_name() failed: -10] -> #28 __libc_start_main[0x7fe47c835ce0] -> #29 _start[0x561b58c4bf30] A friend kindly noted that upstream commit https://github.com/dovecot/core/commit/3ff6022baa757583faf579251fc40 may fix this problem. I applied it to 2.4.1+dfsg1-6+deb13u6 and this did indeed fix the problem. -- Package-specific info: dovecot configuration --------------------- # 2.4.1-4 (7d8c0e5759): /etc/dovecot/dovecot.conf # Pigeonhole version 2.4.1-4 (0a86619f) # OS: Linux 6.12.101+deb13-amd64 x86_64 Debian 13.6 # Hostname: swiss.chard.org # 4 default setting changes since version 2.4.0 dovecot_config_version = 2.4.0 auth_username_format = %{user|username|lower} auth_verbose = yes dovecot_storage_version = 2.4.0 fts_autoindex = yes fts_autoindex_max_recent_msgs = 999 fts_search_add_missing = yes log_path = /var/log/dovecot log_timestamp = "%Y-%m-%d %H:%M:%S " mail_driver = mbox mail_home = /home/%{user | username} mail_inbox_path = /var/mail/%{user} mail_path = %{home}/mail mail_privileged_group = mail protocols { imap = yes } ssl = required ssl_cipher_list = ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305 passdb pam { driver = pam } userdb passwd { driver = passwd } namespace inbox { inbox = yes mailbox Drafts { special_use = "\\Drafts" } mailbox Junk { special_use = "\\Junk" } mailbox Trash { special_use = "\\Trash" } mailbox Sent { special_use = "\\Sent" } mailbox "Sent Messages" { special_use = "\\Sent" } } service imap-login { inet_listener imap { port = 0 } inet_listener imaps { } } service auth { unix_listener auth-userdb { } unix_listener /var/spool/postfix/private/auth { group = postfix mode = 0660 user = postfix } } service auth-worker { } service stats { fifo_listener stats-mail { mode = 0666 } unix_listener stats { mode = 0666 } } ssl_server { cert_file = [redacted] dh_file = /etc/dovecot/dh.pem key_file = [redacted] prefer_ciphers = client } protocol imap { mail_max_userip_connections = 100 } -- System Information: Debian Release: 13.6 APT prefers stable-updates APT policy: (500, 'stable-updates'), (500, 'stable-security'), (500, 'stable') Architecture: amd64 (x86_64) Kernel: Linux 6.12.101+deb13-amd64 (SMP w/2 CPU threads; PREEMPT) Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en_GB:en Shell: /bin/sh linked to /usr/bin/dash Init: systemd (via /run/systemd/system) LSM: SELinux: enabled - Mode: Permissive - Policy name: default Versions of packages dovecot-imapd depends on: ii dovecot-core 1:2.4.1+dfsg1-6+deb13u6 ii libbz2-1.0 1.0.8-6 ii libc6 2.41-12+deb13u3 ii liblz4-1 1.10.0-4 ii libzstd1 1.5.7+dfsg-1 ii ucf 3.0052 ii zlib1g 1:1.3.dfsg+really1.3.1-1+b1 dovecot-imapd recommends no packages. Versions of packages dovecot-imapd suggests: pn ufw <none> Versions of packages dovecot-imapd is related to: ii dovecot-core [dovecot-common] 1:2.4.1+dfsg1-6+deb13u6 pn dovecot-dev <none> pn dovecot-gssapi <none> ii dovecot-imapd 1:2.4.1+dfsg1-6+deb13u6 pn dovecot-ldap <none> pn dovecot-lmtpd <none> pn dovecot-managesieved <none> pn dovecot-mysql <none> pn dovecot-pgsql <none> pn dovecot-pop3d <none> ii dovecot-sieve 1:2.4.1+dfsg1-6+deb13u6 pn dovecot-sqlite <none> -- no debconf information
