A buffer overflow can occur in the Skia library during buffer offset calculations with hardware accelerated canvas 2D actions due to the use of 32-bit calculations instead of 64-bit. This results in a potentially exploitable crash.
External Reference:
https://www.mozilla.org/en-US/security/advisories/mfsa2018-30/#CVE-2018-18493
Statement:
In general, this flaw be exploited through email in the Thunderbird product because scripting is disabled when reading mail, but are potentially risks in browser or browser-like contexts.