1. Multiple vulnerabilities were found in Mozilla Thunderbird. Malicious users can exploit these vulnerabilities to cause denial of service, execute arbitrary code.

   Below is a complete list of vulnerabilities:

   1. Use-after-free vulnerability can be exploited remotely via specially designed HTML5 stream to cause denial of service.
   2. Inter-process Communication (IPC) vulnerability can be exploited remotely via attempt to communicate with the IPC object without validation to bypass security restrictions.
   3. Use-after-free vulnerability in the Libical libary in Thunderbird can be exploited remotely via a specially designed ICS calendar to cause a denial of service.
   4. Multiple memory corruption vulnerabilities can be exploited remotely to execute arbitrary code.

Mozilla Thunderbird earlier than 60.5

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Mozilla Foundation Security Advisory 2019-03

Malware exists for this vulnerability. Usually such malware is classified as Exploit. More details.