# CVE-2016-9584: libical use-after-free in iCalendar parser

Source: https://junglewise.ai/threats/cve-2016-9584-libical-use-after-free-in-icalendar-parser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-01-18. Updated: 2026-05-13  
License: CC BY 4.0 with a link back

CVE-2016-9584 · Severity: critical · CVSS 9.1 · Published 2017-01-18

libical is a widely used open-source library for handling calendar data (iCalendar files). A vulnerability in this library allows an attacker to send a specially crafted calendar file that can crash applications or potentially allow the attacker to read sensitive information from the computer's memory. This could lead to service outages or the exposure of private data handled by email clients and calendar applications.

Technologies: [Libical Project Libical](https://junglewise.ai/threats/technologies/libical). Vendors: [Libical Project](https://junglewise.ai/threats/vendors/libical-project).

## Quick answers

**Is CVE-2016-9584 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-9584 being exploited in the wild.

**How severe is CVE-2016-9584?** Critical severity, with a CVSS score of 9.1, published 18 January 2017.

**Which products and versions are affected?** libical project libical 2.0 and earlier.

**Is there a fix for CVE-2016-9584?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2016-9584 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2016-9584?** Check whether you run Libical Project Libical. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A use-after-free vulnerability exists in libical (specifically identified in version 2.0 and earlier) within the handling of iCalendar (.ics) files. The flaw is triggered during the parsing of crafted calendar components, specifically involving functions like icalreqstattype_as_string_r and icalvalue_as_ical_string_r. A remote attacker can exploit this by providing a malicious .ics file to an application using the library. Successful exploitation can result in a denial of service (application crash) or an information leak where the attacker can read significant portions of heap memory. The vulnerability was confirmed via AddressSanitizer reports showing a READ of freed memory during string conversion processes.

## Affected products

- libical project libical 2.0 and earlier

## Timeline

- 2016-12-15: disclosed: Public disclosure on oss-security mailing list
- 2017-01-18: advisory: NVD publication date

## References

- [http://www.openwall.com/lists/oss-security/2016/12/15/5](http://www.openwall.com/lists/oss-security/2016/12/15/5)
- [http://www.securityfocus.com/bid/94948](http://www.securityfocus.com/bid/94948)

## Related threats

- [libical out-of-bounds read in icaltime_from_string](https://junglewise.ai/threats/cve-2016-5827-libical-out-of-bounds-read-in-icaltime-from-string)
- [libical out-of-bounds read in parser_get_next_char](https://junglewise.ai/threats/cve-2016-5826-libical-out-of-bounds-read-in-parser-get-next-char)
- [libical out-of-bounds read in icalparser_parse_string](https://junglewise.ai/threats/cve-2016-5825-libical-out-of-bounds-read-in-icalparser-parse-string)
- [libical use-after-free in iCalendar parsing](https://junglewise.ai/threats/cve-2016-5824-libical-use-after-free-in-icalendar-parsing)
- [libical use-after-free in icalproperty_new_clone](https://junglewise.ai/threats/cve-2016-5823-libical-use-after-free-in-icalproperty-new-clone)