dovecot crash with Panic: file istream-header-filter.c: line 663

Timo Sirainen timo at
Mon Mar 13 09:01:35 UTC 2023

On 12. Mar 2023, at 20.17, Patrick Mansfield <patmans at> wrote:
> Mar 12 10:32:27 goffin dovecot[8269]: imap(patman)<8452><r+ynYLf2PrDAqAEE>: Panic: file istream-header-filter.c: line 663 (i_stream_header_filter_snapshot_free): assertion failed: (snapshot->mstream->snapshot_pending)

This is unfortunately rather difficult to debug. First you should find out which folder and mail this is happening in. You can do that with gdb:

> #16 0x00007fa3849aa60a in index_mail_parse_headers_internal (mail=mail at entry=0x56150ea5fc78, headers=headers at entry=0x0) at index/index-mail-headers.c:465

fr 16
p mail.uid

Likely deleting that mail manually from the mbox will fix it. Of course, it would be nice if we were able to reproduce the bug also. Once you've found the broken folder, could you anonymize the mbox file contents and send it to me privately? can help you do it. Although I'm not sure if even that is enough to reproduce the bug - might need the dovecot.index* files also but those contain cached headers from the emails, which can be rather sensitive data.

Other things besides deleting the mail that might help, and would be useful to know whether they help:

 * doveadm fetch -u user imap.bodystructure mailbox $folder uid $uid
 * doveadm mailbox cache remove -u user mailbox $folder uid $uid

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