X41 D-Sec GmbH Security Advisory: X41-2019-004
Severity Rating: Medium
Confirmed Affected Versions: All versions affected
Confirmed Patched Versions: Thunderbird ESR 60.7.XXX
Vendor URL: https://www.thunderbird.net/
Vendor Reference: https://bugzilla.mozilla.org/show_bug.cgi?id=1555646
Vector: Incoming mail with calendar attachment
Credit: X41 D-SEC GmbH, Luis Merino
CVSS Score: 6.5
CVSS Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O
A type confusion has been identified in the Thunderbird email client. The issue is present in the libical implementation, which was forked from upstream libical version 0.47.
The issue can be triggered remotely, when an attacker sends an specially crafted calendar attachment and does not require user interaction. It might be used by a remote attacker to crash the process or leak information from the client system via calendar replies.
X41 did not perform a full test or audit on the software.
Thunderbird is a free and open source email, newsfeed, chat, and calendaring client, that's easy to set up and customize.
A type confusion in icalproperty.c
can be triggered while parsing a malformed calendar attachment. Missing
sanity checks allows a TZID property to be parsed as ICAL_FLOAT_VALUE
but it is later used as a string.
The bug manifests with
strdup(tzid); being called with
a bad pointer obtained by casting to
char* from a
float value, which
typically means segfaulting by dereferencing a non-mapped memory page.
An attacker might be able to deliver an input file containing specially crafted float values as TZID properties which could point to arbitrary memory positions. Certain conditions could allow to exfiltrate information via a calendar reply or other undetermined impact.
A reproducer eml file can be found in https://github.com/x41sec/advisories/tree/master/X41-2019-004
2019-05-30 Issues reported to the vendor
2019-06-07 Vendor reply
2019-06-12 CVE IDs assigned
2019-06-13 Patched Version released
2019-06-13 Advisory released
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