Malformed From: triggering segfault in libicui18n.so

[artnocdev]

Roundcube Version: 1.5.2 -> current
PHP 7.4.30
Centos 7.9
apache httpd-2.4.54 - php-fpm

When attemptying to display an email in any list view pane which contains a malformed From header, typically:

=?UTF-8?Q?Redacted_Redacted?= =?UTF-8?Q?_=D2=93=E1=B4=84=C9=AA=E1=B4=8D?=
=?UTF-8?Q?_=E1=B4=8D=E1=B4=84=C9=AA=E1=B4=98=CA=80?=
=?UTF-8?Q?_=E1=B4=8D=C9=AA=C9=B4s?=
=?UTF-8?Q?=E1=B4=9B=CA=9F=E1=B4=8D=E2=80=8C=E2=80=8C_?=
=?UTF-8?Q?via_LinkedIn?= <newsletters-n

this causes a segfault in libicui18n.so:

webmail1 kernel: php-fpm[32302]: segfault at 0 ip 00007f07fd323ce0 sp 00007fff305d4870 error 4 in libicui18n.so.50.2[7f07fd1a5000+1f0000]

Roundcube displays the generic 'Server Error: Service Unavailable' message.

We have since tested on Roundcube 1.4.5 and the same email containing the malformed From address is handled fine.

Thanks.

[artnocdev]

A simpler example. Punnycode -> cyrillic conversion -> display triggers the same segfault:

From: "Redacted Redacted" <admin@contact.xn----7sba4aqieegbiq0e9bxbi8b.ru.com>