Executive brief
libical is a widely used open-source library for handling calendar data (iCalendar files). A vulnerability in how it processes calendar files allows an attacker to crash applications that use this library, such as email clients or calendar apps, by sending a specially crafted invitation or calendar file. This results in a denial of service, potentially disrupting scheduling and communication services.
Technical details
A heap-based out-of-bounds read exists in libical versions 0.47 and 1.0 within the icalparser_parse_string function. The root cause is located in the icalmemory_strdup_and_dequote helper function, which fails to properly validate buffer boundaries when processing malformed iCalendar (.ics) files, specifically those with repeated or improperly terminated TZNAME properties. An attacker can exploit this by providing a crafted .ics file to an application linked against libical (such as Mozilla Thunderbird/Lightning). Successful exploitation results in an application crash (SIGSEGV), leading to a denial of service. While the NVD classifies the vector as Local with User Interaction, the practical delivery via email or calendar subscriptions often gives it a remote delivery profile.
Affected products
- libical project libical 0.47, 1.0
Timeline
- 2016-06-25: disclosed: Public discussion on oss-security mailing list
- 2017-01-27: advisory: NVD publication date