#1101837 /usr/sbin/exim4: Segfault (SIGSEGV, SEGV_MAPERR) only when sending to icloud.com domains and on a blacklist

Package:
exim4-daemon-light
Source:
exim4-daemon-light
Description:
lightweight Exim MTA (v4) daemon
Submitter:
James Lawrie
Date:
2026-06-11 14:53:01 UTC
Severity:
normal
#1101837#5
Date:
2025-04-01 14:13:20 UTC
From:
To:
Dear Maintainer,

We had a strange issue where sending email to *@icloud.com emails caused
a segfault if we were rejected by Proof Point blocklist.

This was only happening for icloud.com, and as soon as we were off the
blacklist the segfault issue went away,

Given difficulty to replicate this scenario (blacklist addition) I
cannot provide further debug output/investigation - I'm only reporting
because of the errors looking like a possible overflow.

2025-04-01 13:04:39 1tyEsu-002hOZ-2M Unfrozen by forced delivery
2025-04-01 13:04:41 1tyEsu-002hOZ-2M H=mx01.mail.icloud.com [17.57.152.5]: SMTP error from remote mail server after RCPT TO:<REMOVED@icloud.com>: 554 5.7.0 Blocked - see https://support.proofpoint.com/dnsbl-lookup.cgi?ip=XX.XX.XX.XX
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SIGSEGV (fault address: 0x17c)
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SIGSEGV (fault address: 0x17c)
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SEGV_MAPERR
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SEGV_MAPERR
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SIGSEGV (null pointer indirection)
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SIGSEGV (null pointer indirection)
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SIGSEGV (2042910 delivering 1tyEsu-002hOZ-2M to mx01.mail.icloud.com [17.57.155.25] (REMOVED@icloud.com)
)
2025-04-01 13:04:42 1tyEsu-002hOZ-2M SIGSEGV (2042910 delivering 1tyEsu-002hOZ-2M to mx01.mail.icloud.com [17.57.155.25] (REMOVED@icloud.com)
)
2025-04-01 13:04:42 1tyEsu-002hOZ-2M Delivery status for REMOVED@icloud.com: got 0 of 7 bytes (pipeheader) from transport process 2042910 for transport smtp

2025-04-01 13:04:42 1tyEsu-002hOZ-2M Delivery status for REMOVED@icloud.com: got 0 of 7 bytes (pipeheader) from transport process 2042910 for transport smtp

2025-04-01 13:04:42 1tyEsu-002hOZ-2M == REMOVED@icloud.com R=dnslookup T=remote_smtp defer (-1): smtp transport process returned non-zero status 0x000b: terminated by signal 11
2025-04-01 13:04:42 1tzaME-008ZSC-1F <= <> R=1tyEsu-002hOZ-2M U=Debian-exim P=local S=773
2025-04-01 13:04:42 1tyEsu-002hOZ-2M Frozen

All other emails went out (or bounced) fine.
#1101837#10
Date:
2026-06-11 14:42:30 UTC
From:
To:
More than one year later, on Exim version 4.96 #2 built 27-May-2026 16:52:26, I can confirm the same exact issue is still here.