# CVE-2016-5826: libical out-of-bounds read in parser_get_next_char

Source: https://junglewise.ai/threats/cve-2016-5826-libical-out-of-bounds-read-in-parser-get-next-char  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2017-01-27. Updated: 2026-05-13  
License: CC BY 4.0 with a link back

CVE-2016-5826 · Severity: high · CVSS 7.5 · Published 2017-01-27

A vulnerability in the libical library, which handles calendar data, could allow an attacker to crash applications that process calendar files. By sending a specially crafted calendar string, a remote attacker can trigger a memory error that causes the service or application to stop responding. This primarily impacts the availability of systems using this library, such as email clients or calendar servers.

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

## Quick answers

**Is CVE-2016-5826 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2016-5826 being exploited in the wild.

**How severe is CVE-2016-5826?** High severity, with a CVSS score of 7.5, published 27 January 2017.

**Which products and versions are affected?** Libical Project Libical 0.47, 1.0; Mozilla Thunderbird unspecified.

**Is there a fix for CVE-2016-5826?** 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-2016-5826 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2016-5826?** Check whether you run Libical Project Libical or Mozilla Thunderbird at an affected version. 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

An out-of-bounds (OOB) heap read exists in the 'parser_get_next_char' function within libical versions 0.47 and 1.0. The vulnerability is triggered when the 'icalparser_parse_string' function processes a specially crafted iCalendar (.ics) string, leading to a memory access violation. An attacker can exploit this remotely without authentication by providing malicious calendar data to an application utilizing the library (such as Mozilla Thunderbird's Lightning component). While primarily resulting in a denial of service (crash), OOB reads can sometimes be leveraged to bypass memory mitigations. The issue was tracked by Mozilla as a low-severity risk for Thunderbird but remains a high-severity DoS for the underlying library.

## Affected products

- libical project libical 0.47, 1.0
- Mozilla Thunderbird unspecified

## Timeline

- 2016-06-25: disclosed: Public discussion on oss-security mailing list
- 2017-01-27: advisory: NVD publication date

## References

- [http://www.openwall.com/lists/oss-security/2016/06/25/4](http://www.openwall.com/lists/oss-security/2016/06/25/4)
- [http://www.securityfocus.com/bid/91459](http://www.securityfocus.com/bid/91459)
- [https://bugzilla.mozilla.org/show_bug.cgi?id=1281041](https://bugzilla.mozilla.org/show_bug.cgi?id=1281041)

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